Garbage collect experimental pollers

6 files changed, 0 insertions, 3207 deletions

diff --git a/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c b/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c
deleted file mode 100644
index e2e3cd9003..0000000000
--- a/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c
+++ /dev/null
@@ -1,1961 +0,0 @@
-/*
- *
- * Copyright 2017 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#include "src/core/lib/iomgr/port.h"
-
-/* This polling engine is only relevant on linux kernels supporting epoll() */
-#ifdef GRPC_LINUX_EPOLL
-
-#include "src/core/lib/iomgr/ev_epoll_limited_pollers_linux.h"
-
-#include <assert.h>
-#include <errno.h>
-#include <limits.h>
-#include <poll.h>
-#include <pthread.h>
-#include <signal.h>
-#include <string.h>
-#include <sys/epoll.h>
-#include <sys/socket.h>
-#include <unistd.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-#include <grpc/support/string_util.h>
-#include <grpc/support/tls.h>
-#include <grpc/support/useful.h>
-
-#include "src/core/lib/debug/stats.h"
-#include "src/core/lib/debug/trace.h"
-#include "src/core/lib/iomgr/ev_posix.h"
-#include "src/core/lib/iomgr/iomgr_internal.h"
-#include "src/core/lib/iomgr/lockfree_event.h"
-#include "src/core/lib/iomgr/timer.h"
-#include "src/core/lib/iomgr/wakeup_fd_posix.h"
-#include "src/core/lib/profiling/timers.h"
-#include "src/core/lib/support/block_annotate.h"
-#include "src/core/lib/support/env.h"
-
-#define GRPC_POLLING_TRACE(fmt, ...)        \
-  if (GRPC_TRACER_ON(grpc_polling_trace)) { \
-    gpr_log(GPR_INFO, (fmt), __VA_ARGS__);  \
-  }
-
-#define GRPC_POLLSET_KICK_BROADCAST ((grpc_pollset_worker *)1)
-
-/* The maximum number of polling threads per polling island. By default no
-   limit */
-static int g_max_pollers_per_pi = INT_MAX;
-
-static int grpc_wakeup_signal = -1;
-static bool is_grpc_wakeup_signal_initialized = false;
-
-/* Implements the function defined in grpc_posix.h. This function might be
- * called before even calling grpc_init() to set either a different signal to
- * use. If signum == -1, then the use of signals is disabled */
-static void grpc_use_signal(int signum) {
-  grpc_wakeup_signal = signum;
-  is_grpc_wakeup_signal_initialized = true;
-
-  if (grpc_wakeup_signal < 0) {
-    gpr_log(GPR_INFO,
-            "Use of signals is disabled. Epoll engine will not be used");
-  } else {
-    gpr_log(GPR_INFO, "epoll engine will be using signal: %d",
-            grpc_wakeup_signal);
-  }
-}
-
-struct polling_island;
-
-typedef enum {
-  POLL_OBJ_FD,
-  POLL_OBJ_POLLSET,
-  POLL_OBJ_POLLSET_SET
-} poll_obj_type;
-
-typedef struct poll_obj {
-#ifndef NDEBUG
-  poll_obj_type obj_type;
-#endif
-  gpr_mu mu;
-  struct polling_island *pi;
-} poll_obj;
-
-static const char *poll_obj_string(poll_obj_type po_type) {
-  switch (po_type) {
-    case POLL_OBJ_FD:
-      return "fd";
-    case POLL_OBJ_POLLSET:
-      return "pollset";
-    case POLL_OBJ_POLLSET_SET:
-      return "pollset_set";
-  }
-
-  GPR_UNREACHABLE_CODE(return "UNKNOWN");
-}
-
-/*******************************************************************************
- * Fd Declarations
- */
-
-#define FD_FROM_PO(po) ((grpc_fd *)(po))
-
-struct grpc_fd {
-  poll_obj po;
-
-  int fd;
-  /* refst format:
-       bit 0    : 1=Active / 0=Orphaned
-       bits 1-n : refcount
-     Ref/Unref by two to avoid altering the orphaned bit */
-  gpr_atm refst;
-
-  /* The fd is either closed or we relinquished control of it. In either
-     cases, this indicates that the 'fd' on this structure is no longer
-     valid */
-  bool orphaned;
-
-  gpr_atm read_closure;
-  gpr_atm write_closure;
-
-  struct grpc_fd *freelist_next;
-  grpc_closure *on_done_closure;
-
-  /* The pollset that last noticed that the fd is readable. The actual type
-   * stored in this is (grpc_pollset *) */
-  gpr_atm read_notifier_pollset;
-
-  grpc_iomgr_object iomgr_object;
-};
-
-/* Reference counting for fds */
-#ifndef NDEBUG
-static void fd_ref(grpc_fd *fd, const char *reason, const char *file, int line);
-static void fd_unref(grpc_fd *fd, const char *reason, const char *file,
-                     int line);
-#define GRPC_FD_REF(fd, reason) fd_ref(fd, reason, __FILE__, __LINE__)
-#define GRPC_FD_UNREF(fd, reason) fd_unref(fd, reason, __FILE__, __LINE__)
-#else
-static void fd_ref(grpc_fd *fd);
-static void fd_unref(grpc_fd *fd);
-#define GRPC_FD_REF(fd, reason) fd_ref(fd)
-#define GRPC_FD_UNREF(fd, reason) fd_unref(fd)
-#endif
-
-static void fd_global_init(void);
-static void fd_global_shutdown(void);
-
-/*******************************************************************************
- * Polling island Declarations
- */
-
-#ifndef NDEBUG
-
-#define PI_ADD_REF(p, r) pi_add_ref_dbg((p), (r), __FILE__, __LINE__)
-#define PI_UNREF(exec_ctx, p, r) \
-  pi_unref_dbg((exec_ctx), (p), (r), __FILE__, __LINE__)
-
-#else
-
-#define PI_ADD_REF(p, r) pi_add_ref((p))
-#define PI_UNREF(exec_ctx, p, r) pi_unref((exec_ctx), (p))
-
-#endif
-
-typedef struct worker_node {
-  struct worker_node *next;
-  struct worker_node *prev;
-} worker_node;
-
-/* This is also used as grpc_workqueue (by directly casing it) */
-typedef struct polling_island {
-  gpr_mu mu;
-  /* Ref count. Use PI_ADD_REF() and PI_UNREF() macros to increment/decrement
-     the refcount.
-     Once the ref count becomes zero, this structure is destroyed which means
-     we should ensure that there is never a scenario where a PI_ADD_REF() is
-     racing with a PI_UNREF() that just made the ref_count zero. */
-  gpr_atm ref_count;
-
-  /* Pointer to the polling_island this merged into.
-   * merged_to value is only set once in polling_island's lifetime (and that too
-   * only if the island is merged with another island). Because of this, we can
-   * use gpr_atm type here so that we can do atomic access on this and reduce
-   * lock contention on 'mu' mutex.
-   *
-   * Note that if this field is not NULL (i.e not 0), all the remaining fields
-   * (except mu and ref_count) are invalid and must be ignored. */
-  gpr_atm merged_to;
-
-  /* Number of threads currently polling on this island */
-  gpr_atm poller_count;
-
-  /* The list of workers waiting to do polling on this polling island */
-  gpr_mu worker_list_mu;
-  worker_node worker_list_head;
-
-  /* The fd of the underlying epoll set */
-  int epoll_fd;
-
-  /* The file descriptors in the epoll set */
-  size_t fd_cnt;
-  size_t fd_capacity;
-  grpc_fd **fds;
-} polling_island;
-
-/*******************************************************************************
- * Pollset Declarations
- */
-#define WORKER_FROM_WORKER_LIST_NODE(p)          \
-  (struct grpc_pollset_worker *)(((char *)(p)) - \
-                                 offsetof(grpc_pollset_worker, pi_list_link))
-struct grpc_pollset_worker {
-  /* Thread id of this worker */
-  pthread_t pt_id;
-
-  /* Used to prevent a worker from getting kicked multiple times */
-  gpr_atm is_kicked;
-
-  struct grpc_pollset_worker *next;
-  struct grpc_pollset_worker *prev;
-
-  /* Indicates if it is this worker's turn to do epoll */
-  gpr_atm is_polling_turn;
-
-  /* Node in the polling island's worker list. */
-  worker_node pi_list_link;
-};
-
-struct grpc_pollset {
-  poll_obj po;
-
-  grpc_pollset_worker root_worker;
-  bool kicked_without_pollers;
-
-  bool shutting_down;          /* Is the pollset shutting down ? */
-  bool finish_shutdown_called; /* Is the 'finish_shutdown_locked()' called ? */
-  grpc_closure *shutdown_done; /* Called after after shutdown is complete */
-};
-
-/*******************************************************************************
- * Pollset-set Declarations
- */
-struct grpc_pollset_set {
-  poll_obj po;
-};
-
-/*******************************************************************************
- * Common helpers
- */
-
-static bool append_error(grpc_error **composite, grpc_error *error,
-                         const char *desc) {
-  if (error == GRPC_ERROR_NONE) return true;
-  if (*composite == GRPC_ERROR_NONE) {
-    *composite = GRPC_ERROR_CREATE_FROM_COPIED_STRING(desc);
-  }
-  *composite = grpc_error_add_child(*composite, error);
-  return false;
-}
-
-/*******************************************************************************
- * Polling island Definitions
- */
-
-/* The wakeup fd that is used to wake up all threads in a Polling island. This
-   is useful in the polling island merge operation where we need to wakeup all
-   the threads currently polling the smaller polling island (so that they can
-   start polling the new/merged polling island)
-
-   NOTE: This fd is initialized to be readable and MUST NOT be consumed i.e the
-   threads that woke up MUST NOT call grpc_wakeup_fd_consume_wakeup() */
-static grpc_wakeup_fd polling_island_wakeup_fd;
-
-/* The polling island being polled right now.
-   See comments in workqueue_maybe_wakeup for why this is tracked. */
-static __thread polling_island *g_current_thread_polling_island;
-
-/* Forward declaration */
-static void polling_island_delete(grpc_exec_ctx *exec_ctx, polling_island *pi);
-
-#ifdef GRPC_TSAN
-/* Currently TSAN may incorrectly flag data races between epoll_ctl and
-   epoll_wait for any grpc_fd structs that are added to the epoll set via
-   epoll_ctl and are returned (within a very short window) via epoll_wait().
-
-   To work-around this race, we establish a happens-before relation between
-   the code just-before epoll_ctl() and the code after epoll_wait() by using
-   this atomic */
-gpr_atm g_epoll_sync;
-#endif /* defined(GRPC_TSAN) */
-
-static void pi_add_ref(polling_island *pi);
-static void pi_unref(grpc_exec_ctx *exec_ctx, polling_island *pi);
-
-#ifndef NDEBUG
-static void pi_add_ref_dbg(polling_island *pi, const char *reason,
-                           const char *file, int line) {
-  if (GRPC_TRACER_ON(grpc_polling_trace)) {
-    gpr_atm old_cnt = gpr_atm_acq_load(&pi->ref_count);
-    gpr_log(GPR_DEBUG, "Add ref pi: %p, old:%" PRIdPTR " -> new:%" PRIdPTR
-                       " (%s) - (%s, %d)",
-            pi, old_cnt, old_cnt + 1, reason, file, line);
-  }
-  pi_add_ref(pi);
-}
-
-static void pi_unref_dbg(grpc_exec_ctx *exec_ctx, polling_island *pi,
-                         const char *reason, const char *file, int line) {
-  if (GRPC_TRACER_ON(grpc_polling_trace)) {
-    gpr_atm old_cnt = gpr_atm_acq_load(&pi->ref_count);
-    gpr_log(GPR_DEBUG, "Unref pi: %p, old:%" PRIdPTR " -> new:%" PRIdPTR
-                       " (%s) - (%s, %d)",
-            pi, old_cnt, (old_cnt - 1), reason, file, line);
-  }
-  pi_unref(exec_ctx, pi);
-}
-#endif
-
-static void pi_add_ref(polling_island *pi) {
-  gpr_atm_no_barrier_fetch_add(&pi->ref_count, 1);
-}
-
-static void pi_unref(grpc_exec_ctx *exec_ctx, polling_island *pi) {
-  /* If ref count went to zero, delete the polling island.
-     Note that this deletion not be done under a lock. Once the ref count goes
-     to zero, we are guaranteed that no one else holds a reference to the
-     polling island (and that there is no racing pi_add_ref() call either).
-
-     Also, if we are deleting the polling island and the merged_to field is
-     non-empty, we should remove a ref to the merged_to polling island
-   */
-  if (1 == gpr_atm_full_fetch_add(&pi->ref_count, -1)) {
-    polling_island *next = (polling_island *)gpr_atm_acq_load(&pi->merged_to);
-    polling_island_delete(exec_ctx, pi);
-    if (next != NULL) {
-      PI_UNREF(exec_ctx, next, "pi_delete"); /* Recursive call */
-    }
-  }
-}
-
-static void worker_node_init(worker_node *node) {
-  node->next = node->prev = node;
-}
-
-/* Not thread safe. Do under a list-level lock */
-static void push_back_worker_node(worker_node *head, worker_node *node) {
-  node->next = head;
-  node->prev = head->prev;
-  head->prev->next = node;
-  head->prev = node;
-}
-
-/* Not thread safe. Do under a list-level lock */
-static void remove_worker_node(worker_node *node) {
-  node->next->prev = node->prev;
-  node->prev->next = node->next;
-  /* If node's next and prev point to itself, the node is considered detached
-   * from the list*/
-  node->next = node->prev = node;
-}
-
-/* Not thread safe. Do under a list-level lock */
-static worker_node *pop_front_worker_node(worker_node *head) {
-  worker_node *node = head->next;
-  if (node != head) {
-    remove_worker_node(node);
-  } else {
-    node = NULL;
-  }
-
-  return node;
-}
-
-/* Returns true if the node's next and prev are pointing to itself (which
-   indicates that the node is not in the list */
-static bool is_worker_node_detached(worker_node *node) {
-  return (node->next == node->prev && node->next == node);
-}
-
-/* The caller is expected to hold pi->mu lock before calling this function
- */
-static void polling_island_add_fds_locked(polling_island *pi, grpc_fd **fds,
-                                          size_t fd_count, bool add_fd_refs,
-                                          grpc_error **error) {
-  int err;
-  size_t i;
-  struct epoll_event ev;
-  char *err_msg;
-  const char *err_desc = "polling_island_add_fds";
-
-#ifdef GRPC_TSAN
-  /* See the definition of g_epoll_sync for more context */
-  gpr_atm_rel_store(&g_epoll_sync, (gpr_atm)0);
-#endif /* defined(GRPC_TSAN) */
-
-  for (i = 0; i < fd_count; i++) {
-    ev.events = (uint32_t)(EPOLLIN | EPOLLOUT | EPOLLET);
-    ev.data.ptr = fds[i];
-    err = epoll_ctl(pi->epoll_fd, EPOLL_CTL_ADD, fds[i]->fd, &ev);
-
-    if (err < 0) {
-      if (errno != EEXIST) {
-        gpr_asprintf(
-            &err_msg,
-            "epoll_ctl (epoll_fd: %d) add fd: %d failed with error: %d (%s)",
-            pi->epoll_fd, fds[i]->fd, errno, strerror(errno));
-        append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-        gpr_free(err_msg);
-      }
-
-      continue;
-    }
-
-    if (pi->fd_cnt == pi->fd_capacity) {
-      pi->fd_capacity = GPR_MAX(pi->fd_capacity + 8, pi->fd_cnt * 3 / 2);
-      pi->fds = gpr_realloc(pi->fds, sizeof(grpc_fd *) * pi->fd_capacity);
-    }
-
-    pi->fds[pi->fd_cnt++] = fds[i];
-    if (add_fd_refs) {
-      GRPC_FD_REF(fds[i], "polling_island");
-    }
-  }
-}
-
-/* The caller is expected to hold pi->mu before calling this */
-static void polling_island_add_wakeup_fd_locked(polling_island *pi,
-                                                grpc_wakeup_fd *wakeup_fd,
-                                                grpc_error **error) {
-  struct epoll_event ev;
-  int err;
-  char *err_msg;
-  const char *err_desc = "polling_island_add_wakeup_fd";
-
-  ev.events = (uint32_t)(EPOLLIN | EPOLLET);
-  ev.data.ptr = wakeup_fd;
-  err = epoll_ctl(pi->epoll_fd, EPOLL_CTL_ADD,
-                  GRPC_WAKEUP_FD_GET_READ_FD(wakeup_fd), &ev);
-  if (err < 0 && errno != EEXIST) {
-    gpr_asprintf(&err_msg,
-                 "epoll_ctl (epoll_fd: %d) add wakeup fd: %d failed with "
-                 "error: %d (%s)",
-                 pi->epoll_fd, GRPC_WAKEUP_FD_GET_READ_FD(wakeup_fd), errno,
-                 strerror(errno));
-    append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-    gpr_free(err_msg);
-  }
-}
-
-/* The caller is expected to hold pi->mu lock before calling this function */
-static void polling_island_remove_all_fds_locked(polling_island *pi,
-                                                 bool remove_fd_refs,
-                                                 grpc_error **error) {
-  int err;
-  size_t i;
-  char *err_msg;
-  const char *err_desc = "polling_island_remove_fds";
-
-  for (i = 0; i < pi->fd_cnt; i++) {
-    err = epoll_ctl(pi->epoll_fd, EPOLL_CTL_DEL, pi->fds[i]->fd, NULL);
-    if (err < 0 && errno != ENOENT) {
-      gpr_asprintf(&err_msg,
-                   "epoll_ctl (epoll_fd: %d) delete fds[%zu]: %d failed with "
-                   "error: %d (%s)",
-                   pi->epoll_fd, i, pi->fds[i]->fd, errno, strerror(errno));
-      append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-      gpr_free(err_msg);
-    }
-
-    if (remove_fd_refs) {
-      GRPC_FD_UNREF(pi->fds[i], "polling_island");
-    }
-  }
-
-  pi->fd_cnt = 0;
-}
-
-/* The caller is expected to hold pi->mu lock before calling this function */
-static void polling_island_remove_fd_locked(polling_island *pi, grpc_fd *fd,
-                                            bool is_fd_closed,
-                                            grpc_error **error) {
-  int err;
-  size_t i;
-  char *err_msg;
-  const char *err_desc = "polling_island_remove_fd";
-
-  /* If fd is already closed, then it would have been automatically been removed
-     from the epoll set */
-  if (!is_fd_closed) {
-    err = epoll_ctl(pi->epoll_fd, EPOLL_CTL_DEL, fd->fd, NULL);
-    if (err < 0 && errno != ENOENT) {
-      gpr_asprintf(
-          &err_msg,
-          "epoll_ctl (epoll_fd: %d) del fd: %d failed with error: %d (%s)",
-          pi->epoll_fd, fd->fd, errno, strerror(errno));
-      append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-      gpr_free(err_msg);
-    }
-  }
-
-  for (i = 0; i < pi->fd_cnt; i++) {
-    if (pi->fds[i] == fd) {
-      pi->fds[i] = pi->fds[--pi->fd_cnt];
-      GRPC_FD_UNREF(fd, "polling_island");
-      break;
-    }
-  }
-}
-
-/* Might return NULL in case of an error */
-static polling_island *polling_island_create(grpc_exec_ctx *exec_ctx,
-                                             grpc_fd *initial_fd,
-                                             grpc_error **error) {
-  polling_island *pi = NULL;
-  const char *err_desc = "polling_island_create";
-
-  *error = GRPC_ERROR_NONE;
-
-  pi = gpr_malloc(sizeof(*pi));
-  gpr_mu_init(&pi->mu);
-  pi->fd_cnt = 0;
-  pi->fd_capacity = 0;
-  pi->fds = NULL;
-  pi->epoll_fd = -1;
-
-  gpr_atm_rel_store(&pi->ref_count, 0);
-  gpr_atm_rel_store(&pi->poller_count, 0);
-  gpr_atm_rel_store(&pi->merged_to, (gpr_atm)NULL);
-
-  gpr_mu_init(&pi->worker_list_mu);
-  worker_node_init(&pi->worker_list_head);
-
-  pi->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
-
-  if (pi->epoll_fd < 0) {
-    append_error(error, GRPC_OS_ERROR(errno, "epoll_create1"), err_desc);
-    goto done;
-  }
-
-  if (initial_fd != NULL) {
-    polling_island_add_fds_locked(pi, &initial_fd, 1, true, error);
-  }
-
-done:
-  if (*error != GRPC_ERROR_NONE) {
-    polling_island_delete(exec_ctx, pi);
-    pi = NULL;
-  }
-  return pi;
-}
-
-static void polling_island_delete(grpc_exec_ctx *exec_ctx, polling_island *pi) {
-  GPR_ASSERT(pi->fd_cnt == 0);
-
-  if (pi->epoll_fd >= 0) {
-    close(pi->epoll_fd);
-  }
-  gpr_mu_destroy(&pi->mu);
-  gpr_mu_destroy(&pi->worker_list_mu);
-  GPR_ASSERT(is_worker_node_detached(&pi->worker_list_head));
-
-  gpr_free(pi->fds);
-  gpr_free(pi);
-}
-
-/* Attempts to gets the last polling island in the linked list (liked by the
- * 'merged_to' field). Since this does not lock the polling island, there are no
- * guarantees that the island returned is the last island */
-static polling_island *polling_island_maybe_get_latest(polling_island *pi) {
-  polling_island *next = (polling_island *)gpr_atm_acq_load(&pi->merged_to);
-  while (next != NULL) {
-    pi = next;
-    next = (polling_island *)gpr_atm_acq_load(&pi->merged_to);
-  }
-
-  return pi;
-}
-
-/* Gets the lock on the *latest* polling island i.e the last polling island in
-   the linked list (linked by the 'merged_to' field). Call gpr_mu_unlock on the
-   returned polling island's mu.
-   Usage: To lock/unlock polling island "pi", do the following:
-      polling_island *pi_latest = polling_island_lock(pi);
-      ...
-      ... critical section ..
-      ...
-      gpr_mu_unlock(&pi_latest->mu); // NOTE: use pi_latest->mu. NOT pi->mu */
-static polling_island *polling_island_lock(polling_island *pi) {
-  polling_island *next = NULL;
-
-  while (true) {
-    next = (polling_island *)gpr_atm_acq_load(&pi->merged_to);
-    if (next == NULL) {
-      /* Looks like 'pi' is the last node in the linked list but unless we check
-         this by holding the pi->mu lock, we cannot be sure (i.e without the
-         pi->mu lock, we don't prevent island merges).
-         To be absolutely sure, check once more by holding the pi->mu lock */
-      gpr_mu_lock(&pi->mu);
-      next = (polling_island *)gpr_atm_acq_load(&pi->merged_to);
-      if (next == NULL) {
-        /* pi is infact the last node and we have the pi->mu lock. we're done */
-        break;
-      }
-
-      /* pi->merged_to is not NULL i.e pi isn't the last node anymore. pi->mu
-       * isn't the lock we are interested in. Continue traversing the list */
-      gpr_mu_unlock(&pi->mu);
-    }
-
-    pi = next;
-  }
-
-  return pi;
-}
-
-/* Gets the lock on the *latest* polling islands in the linked lists pointed by
-   *p and *q (and also updates *p and *q to point to the latest polling islands)
-
-   This function is needed because calling the following block of code to obtain
-   locks on polling islands (*p and *q) is prone to deadlocks.
-     {
-       polling_island_lock(*p, true);
-       polling_island_lock(*q, true);
-     }
-
-   Usage/example:
-     polling_island *p1;
-     polling_island *p2;
-     ..
-     polling_island_lock_pair(&p1, &p2);
-     ..
-     .. Critical section with both p1 and p2 locked
-     ..
-     // Release locks: Always call polling_island_unlock_pair() to release locks
-     polling_island_unlock_pair(p1, p2);
-*/
-static void polling_island_lock_pair(polling_island **p, polling_island **q) {
-  polling_island *pi_1 = *p;
-  polling_island *pi_2 = *q;
-  polling_island *next_1 = NULL;
-  polling_island *next_2 = NULL;
-
-  /* The algorithm is simple:
-      - Go to the last polling islands in the linked lists *pi_1 and *pi_2 (and
-        keep updating pi_1 and pi_2)
-      - Then obtain locks on the islands by following a lock order rule of
-        locking polling_island with lower address first
-           Special case: Before obtaining the locks, check if pi_1 and pi_2 are
-           pointing to the same island. If that is the case, we can just call
-           polling_island_lock()
-      - After obtaining both the locks, double check that the polling islands
-        are still the last polling islands in their respective linked lists
-        (this is because there might have been polling island merges before
-        we got the lock)
-      - If the polling islands are the last islands, we are done. If not,
-        release the locks and continue the process from the first step */
-  while (true) {
-    next_1 = (polling_island *)gpr_atm_acq_load(&pi_1->merged_to);
-    while (next_1 != NULL) {
-      pi_1 = next_1;
-      next_1 = (polling_island *)gpr_atm_acq_load(&pi_1->merged_to);
-    }
-
-    next_2 = (polling_island *)gpr_atm_acq_load(&pi_2->merged_to);
-    while (next_2 != NULL) {
-      pi_2 = next_2;
-      next_2 = (polling_island *)gpr_atm_acq_load(&pi_2->merged_to);
-    }
-
-    if (pi_1 == pi_2) {
-      pi_1 = pi_2 = polling_island_lock(pi_1);
-      break;
-    }
-
-    if (pi_1 < pi_2) {
-      gpr_mu_lock(&pi_1->mu);
-      gpr_mu_lock(&pi_2->mu);
-    } else {
-      gpr_mu_lock(&pi_2->mu);
-      gpr_mu_lock(&pi_1->mu);
-    }
-
-    next_1 = (polling_island *)gpr_atm_acq_load(&pi_1->merged_to);
-    next_2 = (polling_island *)gpr_atm_acq_load(&pi_2->merged_to);
-    if (next_1 == NULL && next_2 == NULL) {
-      break;
-    }
-
-    gpr_mu_unlock(&pi_1->mu);
-    gpr_mu_unlock(&pi_2->mu);
-  }
-
-  *p = pi_1;
-  *q = pi_2;
-}
-
-static void polling_island_unlock_pair(polling_island *p, polling_island *q) {
-  if (p == q) {
-    gpr_mu_unlock(&p->mu);
-  } else {
-    gpr_mu_unlock(&p->mu);
-    gpr_mu_unlock(&q->mu);
-  }
-}
-
-static polling_island *polling_island_merge(polling_island *p,
-                                            polling_island *q,
-                                            grpc_error **error) {
-  /* Get locks on both the polling islands */
-  polling_island_lock_pair(&p, &q);
-
-  if (p != q) {
-    /* Make sure that p points to the polling island with fewer fds than q */
-    if (p->fd_cnt > q->fd_cnt) {
-      GPR_SWAP(polling_island *, p, q);
-    }
-
-    /* Merge p with q i.e move all the fds from p (The one with fewer fds) to q
-       Note that the refcounts on the fds being moved will not change here.
-       This is why the last param in the following two functions is 'false') */
-    polling_island_add_fds_locked(q, p->fds, p->fd_cnt, false, error);
-    polling_island_remove_all_fds_locked(p, false, error);
-
-    /* Wakeup all the pollers (if any) on p so that they pickup this change */
-    polling_island_add_wakeup_fd_locked(p, &polling_island_wakeup_fd, error);
-
-    /* Add the 'merged_to' link from p --> q */
-    gpr_atm_rel_store(&p->merged_to, (gpr_atm)q);
-    PI_ADD_REF(q, "pi_merge"); /* To account for the new incoming ref from p */
-  }
-  /* else if p == q, nothing needs to be done */
-
-  polling_island_unlock_pair(p, q);
-
-  /* Return the merged polling island (Note that no merge would have happened
-     if p == q which is ok) */
-  return q;
-}
-
-static grpc_error *polling_island_global_init() {
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  error = grpc_wakeup_fd_init(&polling_island_wakeup_fd);
-  if (error == GRPC_ERROR_NONE) {
-    error = grpc_wakeup_fd_wakeup(&polling_island_wakeup_fd);
-  }
-
-  return error;
-}
-
-static void polling_island_global_shutdown() {
-  grpc_wakeup_fd_destroy(&polling_island_wakeup_fd);
-}
-
-/*******************************************************************************
- * Fd Definitions
- */
-
-/* We need to keep a freelist not because of any concerns of malloc performance
- * but instead so that implementations with multiple threads in (for example)
- * epoll_wait deal with the race between pollset removal and incoming poll
- * notifications.
- *
- * The problem is that the poller ultimately holds a reference to this
- * object, so it is very difficult to know when is safe to free it, at least
- * without some expensive synchronization.
- *
- * If we keep the object freelisted, in the worst case losing this race just
- * becomes a spurious read notification on a reused fd.
- */
-
-/* The alarm system needs to be able to wakeup 'some poller' sometimes
- * (specifically when a new alarm needs to be triggered earlier than the next
- * alarm 'epoch'). This wakeup_fd gives us something to alert on when such a
- * case occurs. */
-
-static grpc_fd *fd_freelist = NULL;
-static gpr_mu fd_freelist_mu;
-
-#ifndef NDEBUG
-#define REF_BY(fd, n, reason) ref_by(fd, n, reason, __FILE__, __LINE__)
-#define UNREF_BY(fd, n, reason) unref_by(fd, n, reason, __FILE__, __LINE__)
-static void ref_by(grpc_fd *fd, int n, const char *reason, const char *file,
-                   int line) {
-  if (GRPC_TRACER_ON(grpc_trace_fd_refcount)) {
-    gpr_log(GPR_DEBUG,
-            "FD %d %p   ref %d %" PRIdPTR " -> %" PRIdPTR " [%s; %s:%d]",
-            fd->fd, fd, n, gpr_atm_no_barrier_load(&fd->refst),
-            gpr_atm_no_barrier_load(&fd->refst) + n, reason, file, line);
-  }
-#else
-#define REF_BY(fd, n, reason) ref_by(fd, n)
-#define UNREF_BY(fd, n, reason) unref_by(fd, n)
-static void ref_by(grpc_fd *fd, int n) {
-#endif
-  GPR_ASSERT(gpr_atm_no_barrier_fetch_add(&fd->refst, n) > 0);
-}
-
-#ifndef NDEBUG
-static void unref_by(grpc_fd *fd, int n, const char *reason, const char *file,
-                     int line) {
-  if (GRPC_TRACER_ON(grpc_trace_fd_refcount)) {
-    gpr_log(GPR_DEBUG,
-            "FD %d %p unref %d %" PRIdPTR " -> %" PRIdPTR " [%s; %s:%d]",
-            fd->fd, fd, n, gpr_atm_no_barrier_load(&fd->refst),
-            gpr_atm_no_barrier_load(&fd->refst) - n, reason, file, line);
-  }
-#else
-static void unref_by(grpc_fd *fd, int n) {
-#endif
-  gpr_atm old = gpr_atm_full_fetch_add(&fd->refst, -n);
-  if (old == n) {
-    /* Add the fd to the freelist */
-    gpr_mu_lock(&fd_freelist_mu);
-    fd->freelist_next = fd_freelist;
-    fd_freelist = fd;
-    grpc_iomgr_unregister_object(&fd->iomgr_object);
-
-    grpc_lfev_destroy(&fd->read_closure);
-    grpc_lfev_destroy(&fd->write_closure);
-
-    gpr_mu_unlock(&fd_freelist_mu);
-  } else {
-    GPR_ASSERT(old > n);
-  }
-}
-
-/* Increment refcount by two to avoid changing the orphan bit */
-#ifndef NDEBUG
-static void fd_ref(grpc_fd *fd, const char *reason, const char *file,
-                   int line) {
-  ref_by(fd, 2, reason, file, line);
-}
-
-static void fd_unref(grpc_fd *fd, const char *reason, const char *file,
-                     int line) {
-  unref_by(fd, 2, reason, file, line);
-}
-#else
-static void fd_ref(grpc_fd *fd) { ref_by(fd, 2); }
-static void fd_unref(grpc_fd *fd) { unref_by(fd, 2); }
-#endif
-
-static void fd_global_init(void) { gpr_mu_init(&fd_freelist_mu); }
-
-static void fd_global_shutdown(void) {
-  gpr_mu_lock(&fd_freelist_mu);
-  gpr_mu_unlock(&fd_freelist_mu);
-  while (fd_freelist != NULL) {
-    grpc_fd *fd = fd_freelist;
-    fd_freelist = fd_freelist->freelist_next;
-    gpr_mu_destroy(&fd->po.mu);
-    gpr_free(fd);
-  }
-  gpr_mu_destroy(&fd_freelist_mu);
-}
-
-static grpc_fd *fd_create(int fd, const char *name) {
-  grpc_fd *new_fd = NULL;
-
-  gpr_mu_lock(&fd_freelist_mu);
-  if (fd_freelist != NULL) {
-    new_fd = fd_freelist;
-    fd_freelist = fd_freelist->freelist_next;
-  }
-  gpr_mu_unlock(&fd_freelist_mu);
-
-  if (new_fd == NULL) {
-    new_fd = gpr_malloc(sizeof(grpc_fd));
-    gpr_mu_init(&new_fd->po.mu);
-  }
-
-  /* Note: It is not really needed to get the new_fd->po.mu lock here. If this
-   * is a newly created fd (or an fd we got from the freelist), no one else
-   * would be holding a lock to it anyway. */
-  gpr_mu_lock(&new_fd->po.mu);
-  new_fd->po.pi = NULL;
-#ifndef NDEBUG
-  new_fd->po.obj_type = POLL_OBJ_FD;
-#endif
-
-  gpr_atm_rel_store(&new_fd->refst, (gpr_atm)1);
-  new_fd->fd = fd;
-  new_fd->orphaned = false;
-  grpc_lfev_init(&new_fd->read_closure);
-  grpc_lfev_init(&new_fd->write_closure);
-  gpr_atm_no_barrier_store(&new_fd->read_notifier_pollset, (gpr_atm)NULL);
-
-  new_fd->freelist_next = NULL;
-  new_fd->on_done_closure = NULL;
-
-  gpr_mu_unlock(&new_fd->po.mu);
-
-  char *fd_name;
-  gpr_asprintf(&fd_name, "%s fd=%d", name, fd);
-  grpc_iomgr_register_object(&new_fd->iomgr_object, fd_name);
-#ifndef NDEBUG
-  if (GRPC_TRACER_ON(grpc_trace_fd_refcount)) {
-    gpr_log(GPR_DEBUG, "FD %d %p create %s", fd, new_fd, fd_name);
-  }
-#endif
-  gpr_free(fd_name);
-  return new_fd;
-}
-
-static int fd_wrapped_fd(grpc_fd *fd) {
-  int ret_fd = -1;
-  gpr_mu_lock(&fd->po.mu);
-  if (!fd->orphaned) {
-    ret_fd = fd->fd;
-  }
-  gpr_mu_unlock(&fd->po.mu);
-
-  return ret_fd;
-}
-
-static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                      grpc_closure *on_done, int *release_fd,
-                      bool already_closed, const char *reason) {
-  grpc_error *error = GRPC_ERROR_NONE;
-  polling_island *unref_pi = NULL;
-
-  gpr_mu_lock(&fd->po.mu);
-  fd->on_done_closure = on_done;
-
-  /* Remove the active status but keep referenced. We want this grpc_fd struct
-     to be alive (and not added to freelist) until the end of this function */
-  REF_BY(fd, 1, reason);
-
-  /* Remove the fd from the polling island:
-     - Get a lock on the latest polling island (i.e the last island in the
-       linked list pointed by fd->po.pi). This is the island that
-       would actually contain the fd
-     - Remove the fd from the latest polling island
-     - Unlock the latest polling island
-     - Set fd->po.pi to NULL (but remove the ref on the polling island
-       before doing this.) */
-  if (fd->po.pi != NULL) {
-    polling_island *pi_latest = polling_island_lock(fd->po.pi);
-    polling_island_remove_fd_locked(pi_latest, fd, already_closed, &error);
-    gpr_mu_unlock(&pi_latest->mu);
-
-    unref_pi = fd->po.pi;
-    fd->po.pi = NULL;
-  }
-
-  /* If release_fd is not NULL, we should be relinquishing control of the file
-     descriptor fd->fd (but we still own the grpc_fd structure). */
-  if (release_fd != NULL) {
-    *release_fd = fd->fd;
-  } else {
-    close(fd->fd);
-  }
-
-  fd->orphaned = true;
-
-  GRPC_CLOSURE_SCHED(exec_ctx, fd->on_done_closure, GRPC_ERROR_REF(error));
-
-  gpr_mu_unlock(&fd->po.mu);
-  UNREF_BY(fd, 2, reason); /* Drop the reference */
-  if (unref_pi != NULL) {
-    /* Unref stale polling island here, outside the fd lock above.
-       The polling island owns a workqueue which owns an fd, and unreffing
-       inside the lock can cause an eventual lock loop that makes TSAN very
-       unhappy. */
-    PI_UNREF(exec_ctx, unref_pi, "fd_orphan");
-  }
-  GRPC_LOG_IF_ERROR("fd_orphan", GRPC_ERROR_REF(error));
-  GRPC_ERROR_UNREF(error);
-}
-
-static grpc_pollset *fd_get_read_notifier_pollset(grpc_exec_ctx *exec_ctx,
-                                                  grpc_fd *fd) {
-  gpr_atm notifier = gpr_atm_acq_load(&fd->read_notifier_pollset);
-  return (grpc_pollset *)notifier;
-}
-
-static bool fd_is_shutdown(grpc_fd *fd) {
-  return grpc_lfev_is_shutdown(&fd->read_closure);
-}
-
-/* Might be called multiple times */
-static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_error *why) {
-  if (grpc_lfev_set_shutdown(exec_ctx, &fd->read_closure,
-                             GRPC_ERROR_REF(why))) {
-    shutdown(fd->fd, SHUT_RDWR);
-    grpc_lfev_set_shutdown(exec_ctx, &fd->write_closure, GRPC_ERROR_REF(why));
-  }
-  GRPC_ERROR_UNREF(why);
-}
-
-static void fd_notify_on_read(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                              grpc_closure *closure) {
-  grpc_lfev_notify_on(exec_ctx, &fd->read_closure, closure, "read");
-}
-
-static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                               grpc_closure *closure) {
-  grpc_lfev_notify_on(exec_ctx, &fd->write_closure, closure, "write");
-}
-
-/*******************************************************************************
- * Pollset Definitions
- */
-GPR_TLS_DECL(g_current_thread_pollset);
-GPR_TLS_DECL(g_current_thread_worker);
-static __thread bool g_initialized_sigmask;
-static __thread sigset_t g_orig_sigmask;
-static __thread sigset_t g_wakeup_sig_set;
-
-static void sig_handler(int sig_num) {
-#ifdef GRPC_EPOLL_DEBUG
-  gpr_log(GPR_INFO, "Received signal %d", sig_num);
-#endif
-}
-
-static void pollset_worker_init(grpc_pollset_worker *worker) {
-  worker->pt_id = pthread_self();
-  worker->next = worker->prev = NULL;
-  gpr_atm_no_barrier_store(&worker->is_kicked, (gpr_atm)0);
-  gpr_atm_no_barrier_store(&worker->is_polling_turn, (gpr_atm)0);
-  worker_node_init(&worker->pi_list_link);
-}
-
-static void poller_kick_init() { signal(grpc_wakeup_signal, sig_handler); }
-
-/* Global state management */
-static grpc_error *pollset_global_init(void) {
-  gpr_tls_init(&g_current_thread_pollset);
-  gpr_tls_init(&g_current_thread_worker);
-  poller_kick_init();
-  return GRPC_ERROR_NONE;
-}
-
-static void pollset_global_shutdown(void) {
-  gpr_tls_destroy(&g_current_thread_pollset);
-  gpr_tls_destroy(&g_current_thread_worker);
-}
-
-static grpc_error *worker_kick(grpc_pollset_worker *worker,
-                               gpr_atm *is_kicked) {
-  grpc_error *err = GRPC_ERROR_NONE;
-
-  /* Kick the worker only if it was not already kicked */
-  if (gpr_atm_no_barrier_cas(is_kicked, (gpr_atm)0, (gpr_atm)1)) {
-    GRPC_POLLING_TRACE(
-        "pollset_worker_kick: Kicking worker: %p (thread id: %ld)",
-        (void *)worker, (long int)worker->pt_id);
-    int err_num = pthread_kill(worker->pt_id, grpc_wakeup_signal);
-    if (err_num != 0) {
-      err = GRPC_OS_ERROR(err_num, "pthread_kill");
-    }
-  }
-  return err;
-}
-
-static grpc_error *pollset_worker_kick(grpc_pollset_worker *worker) {
-  return worker_kick(worker, &worker->is_kicked);
-}
-
-static grpc_error *poller_kick(grpc_pollset_worker *worker) {
-  return worker_kick(worker, &worker->is_polling_turn);
-}
-
-/* Return 1 if the pollset has active threads in pollset_work (pollset must
- * be locked) */
-static int pollset_has_workers(grpc_pollset *p) {
-  return p->root_worker.next != &p->root_worker;
-}
-
-static void remove_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->prev->next = worker->next;
-  worker->next->prev = worker->prev;
-}
-
-static grpc_pollset_worker *pop_front_worker(grpc_pollset *p) {
-  if (pollset_has_workers(p)) {
-    grpc_pollset_worker *w = p->root_worker.next;
-    remove_worker(p, w);
-    return w;
-  } else {
-    return NULL;
-  }
-}
-
-static void push_back_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->next = &p->root_worker;
-  worker->prev = worker->next->prev;
-  worker->prev->next = worker->next->prev = worker;
-}
-
-static void push_front_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->prev = &p->root_worker;
-  worker->next = worker->prev->next;
-  worker->prev->next = worker->next->prev = worker;
-}
-
-/* p->mu must be held before calling this function */
-static grpc_error *pollset_kick(grpc_pollset *p,
-                                grpc_pollset_worker *specific_worker) {
-  GPR_TIMER_BEGIN("pollset_kick", 0);
-  grpc_error *error = GRPC_ERROR_NONE;
-  const char *err_desc = "Kick Failure";
-  grpc_pollset_worker *worker = specific_worker;
-  if (worker != NULL) {
-    if (worker == GRPC_POLLSET_KICK_BROADCAST) {
-      if (pollset_has_workers(p)) {
-        GPR_TIMER_BEGIN("pollset_kick.broadcast", 0);
-        for (worker = p->root_worker.next; worker != &p->root_worker;
-             worker = worker->next) {
-          if (gpr_tls_get(&g_current_thread_worker) != (intptr_t)worker) {
-            append_error(&error, pollset_worker_kick(worker), err_desc);
-          }
-        }
-        GPR_TIMER_END("pollset_kick.broadcast", 0);
-      } else {
-        p->kicked_without_pollers = true;
-      }
-    } else {
-      GPR_TIMER_MARK("kicked_specifically", 0);
-      if (gpr_tls_get(&g_current_thread_worker) != (intptr_t)worker) {
-        append_error(&error, pollset_worker_kick(worker), err_desc);
-      }
-    }
-  } else if (gpr_tls_get(&g_current_thread_pollset) != (intptr_t)p) {
-    /* Since worker == NULL, it means that we can kick "any" worker on this
-       pollset 'p'. If 'p' happens to be the same pollset this thread is
-       currently polling (i.e in pollset_work() function), then there is no need
-       to kick any other worker since the current thread can just absorb the
-       kick. This is the reason why we enter this case only when
-       g_current_thread_pollset is != p */
-
-    GPR_TIMER_MARK("kick_anonymous", 0);
-    worker = pop_front_worker(p);
-    if (worker != NULL) {
-      GPR_TIMER_MARK("finally_kick", 0);
-      push_back_worker(p, worker);
-      append_error(&error, pollset_worker_kick(worker), err_desc);
-    } else {
-      GPR_TIMER_MARK("kicked_no_pollers", 0);
-      p->kicked_without_pollers = true;
-    }
-  }
-
-  GPR_TIMER_END("pollset_kick", 0);
-  GRPC_LOG_IF_ERROR("pollset_kick", GRPC_ERROR_REF(error));
-  return error;
-}
-
-static void pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
-  gpr_mu_init(&pollset->po.mu);
-  *mu = &pollset->po.mu;
-  pollset->po.pi = NULL;
-#ifndef NDEBUG
-  pollset->po.obj_type = POLL_OBJ_POLLSET;
-#endif
-
-  pollset->root_worker.next = pollset->root_worker.prev = &pollset->root_worker;
-  pollset->kicked_without_pollers = false;
-
-  pollset->shutting_down = false;
-  pollset->finish_shutdown_called = false;
-  pollset->shutdown_done = NULL;
-}
-
-/* Convert millis to timespec (clock-type is assumed to be GPR_TIMESPAN) */
-static struct timespec millis_to_timespec(int millis) {
-  struct timespec linux_ts;
-  gpr_timespec gpr_ts;
-
-  if (millis == -1) {
-    gpr_ts = gpr_inf_future(GPR_TIMESPAN);
-  } else {
-    gpr_ts = gpr_time_from_millis(millis, GPR_TIMESPAN);
-  }
-
-  linux_ts.tv_sec = (time_t)gpr_ts.tv_sec;
-  linux_ts.tv_nsec = gpr_ts.tv_nsec;
-  return linux_ts;
-}
-
-/* Convert a timespec to milliseconds:
-   - Very small or negative poll times are clamped to zero to do a non-blocking
-     poll (which becomes spin polling)
-   - Other small values are rounded up to one millisecond
-   - Longer than a millisecond polls are rounded up to the next nearest
-     millisecond to avoid spinning
-   - Infinite timeouts are converted to -1 */
-static int poll_deadline_to_millis_timeout(gpr_timespec deadline,
-                                           gpr_timespec now) {
-  gpr_timespec timeout;
-  static const int64_t max_spin_polling_us = 10;
-  if (gpr_time_cmp(deadline, gpr_inf_future(deadline.clock_type)) == 0) {
-    return -1;
-  }
-
-  if (gpr_time_cmp(deadline, gpr_time_add(now, gpr_time_from_micros(
-                                                   max_spin_polling_us,
-                                                   GPR_TIMESPAN))) <= 0) {
-    return 0;
-  }
-  timeout = gpr_time_sub(deadline, now);
-  int millis = gpr_time_to_millis(gpr_time_add(
-      timeout, gpr_time_from_nanos(GPR_NS_PER_MS - 1, GPR_TIMESPAN)));
-  return millis >= 1 ? millis : 1;
-}
-
-static void fd_become_readable(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                               grpc_pollset *notifier) {
-  grpc_lfev_set_ready(exec_ctx, &fd->read_closure, "read");
-
-  /* Note, it is possible that fd_become_readable might be called twice with
-     different 'notifier's when an fd becomes readable and it is in two epoll
-     sets (This can happen briefly during polling island merges). In such cases
-     it does not really matter which notifer is set as the read_notifier_pollset
-     (They would both point to the same polling island anyway) */
-  /* Use release store to match with acquire load in fd_get_read_notifier */
-  gpr_atm_rel_store(&fd->read_notifier_pollset, (gpr_atm)notifier);
-}
-
-static void fd_become_writable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
-  grpc_lfev_set_ready(exec_ctx, &fd->write_closure, "write");
-}
-
-static void pollset_release_polling_island(grpc_exec_ctx *exec_ctx,
-                                           grpc_pollset *ps, char *reason) {
-  if (ps->po.pi != NULL) {
-    PI_UNREF(exec_ctx, ps->po.pi, reason);
-  }
-  ps->po.pi = NULL;
-}
-
-static void finish_shutdown_locked(grpc_exec_ctx *exec_ctx,
-                                   grpc_pollset *pollset) {
-  /* The pollset cannot have any workers if we are at this stage */
-  GPR_ASSERT(!pollset_has_workers(pollset));
-
-  pollset->finish_shutdown_called = true;
-
-  /* Release the ref and set pollset->po.pi to NULL */
-  pollset_release_polling_island(exec_ctx, pollset, "ps_shutdown");
-  GRPC_CLOSURE_SCHED(exec_ctx, pollset->shutdown_done, GRPC_ERROR_NONE);
-}
-
-/* pollset->po.mu lock must be held by the caller before calling this */
-static void pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                             grpc_closure *closure) {
-  GPR_TIMER_BEGIN("pollset_shutdown", 0);
-  GPR_ASSERT(!pollset->shutting_down);
-  pollset->shutting_down = true;
-  pollset->shutdown_done = closure;
-  pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
-
-  /* If the pollset has any workers, we cannot call finish_shutdown_locked()
-     because it would release the underlying polling island. In such a case, we
-     let the last worker call finish_shutdown_locked() from pollset_work() */
-  if (!pollset_has_workers(pollset)) {
-    GPR_ASSERT(!pollset->finish_shutdown_called);
-    GPR_TIMER_MARK("pollset_shutdown.finish_shutdown_locked", 0);
-    finish_shutdown_locked(exec_ctx, pollset);
-  }
-  GPR_TIMER_END("pollset_shutdown", 0);
-}
-
-/* pollset_shutdown is guaranteed to be called before pollset_destroy. So other
- * than destroying the mutexes, there is nothing special that needs to be done
- * here */
-static void pollset_destroy(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset) {
-  GPR_ASSERT(!pollset_has_workers(pollset));
-  gpr_mu_destroy(&pollset->po.mu);
-}
-
-/* NOTE: This function may modify 'now' */
-static bool acquire_polling_lease(grpc_exec_ctx *exec_ctx,
-                                  grpc_pollset_worker *worker,
-                                  polling_island *pi, gpr_timespec deadline,
-                                  gpr_timespec *now) {
-  bool is_lease_acquired = false;
-
-  gpr_mu_lock(&pi->worker_list_mu);  //  LOCK
-  long num_pollers = gpr_atm_no_barrier_load(&pi->poller_count);
-
-  if (num_pollers >= g_max_pollers_per_pi) {
-    push_back_worker_node(&pi->worker_list_head, &worker->pi_list_link);
-    gpr_mu_unlock(&pi->worker_list_mu);  // UNLOCK
-
-    bool is_timeout = false;
-    int ret;
-    int timeout_ms = poll_deadline_to_millis_timeout(deadline, *now);
-    if (timeout_ms == -1) {
-      ret = sigwaitinfo(&g_wakeup_sig_set, NULL);
-    } else {
-      struct timespec sigwait_timeout = millis_to_timespec(timeout_ms);
-      GRPC_SCHEDULING_START_BLOCKING_REGION;
-      GRPC_STATS_INC_SYSCALL_WAIT(exec_ctx);
-      ret = sigtimedwait(&g_wakeup_sig_set, NULL, &sigwait_timeout);
-      GRPC_SCHEDULING_END_BLOCKING_REGION;
-    }
-
-    if (ret == -1) {
-      if (errno == EAGAIN) {
-        is_timeout = true;
-      } else {
-        /* NOTE: This should not happen. If we see these log messages, it means
-           we are most likely doing something incorrect in the setup * needed
-           for sigwaitinfo/sigtimedwait */
-        gpr_log(GPR_ERROR,
-                "sigtimedwait failed with retcode: %d (timeout_ms: %d)", errno,
-                timeout_ms);
-      }
-    }
-
-    /* Did the worker come out of sigtimedwait due to a thread that just
-       exited epoll and kicking it (in release_polling_lease function). */
-    bool is_polling_turn = gpr_atm_acq_load(&worker->is_polling_turn);
-
-    /* Did the worker come out of sigtimedwait due to a thread alerting it that
-       some completion event was (likely) available in the completion queue */
-    bool is_kicked = gpr_atm_no_barrier_load(&worker->is_kicked);
-
-    if (is_kicked || is_timeout) {
-      *now = deadline; /* Essentially make the epoll timeout = 0 */
-    } else if (is_polling_turn) {
-      *now = gpr_now(GPR_CLOCK_MONOTONIC); /* Reduce the epoll timeout */
-    }
-
-    gpr_mu_lock(&pi->worker_list_mu);  // LOCK
-    /* The node might have already been removed from the list by the poller
-       that kicked this. However it is safe to call 'remove_worker_node' on
-       an already detached node */
-    remove_worker_node(&worker->pi_list_link);
-    /* It is important to read the num_pollers again under the lock so that we
-     * have the latest num_pollers value that doesn't change while we are doing
-     * the "(num_pollers < g_max_pollers_per_pi)" a a few lines below */
-    num_pollers = gpr_atm_no_barrier_load(&pi->poller_count);
-  }
-
-  if (num_pollers < g_max_pollers_per_pi) {
-    gpr_atm_no_barrier_fetch_add(&pi->poller_count, 1);
-    is_lease_acquired = true;
-  }
-
-  gpr_mu_unlock(&pi->worker_list_mu);  // UNLOCK
-  return is_lease_acquired;
-}
-
-static void release_polling_lease(polling_island *pi, grpc_error **error) {
-  gpr_mu_lock(&pi->worker_list_mu);
-
-  gpr_atm_no_barrier_fetch_add(&pi->poller_count, -1);
-  worker_node *node = pop_front_worker_node(&pi->worker_list_head);
-  if (node != NULL) {
-    grpc_pollset_worker *next_worker = WORKER_FROM_WORKER_LIST_NODE(node);
-    append_error(error, poller_kick(next_worker), "poller kick error");
-  }
-
-  gpr_mu_unlock(&pi->worker_list_mu);
-}
-
-#define GRPC_EPOLL_MAX_EVENTS 100
-static void pollset_do_epoll_pwait(grpc_exec_ctx *exec_ctx, int epoll_fd,
-                                   grpc_pollset *pollset, polling_island *pi,
-                                   grpc_pollset_worker *worker,
-                                   gpr_timespec now, gpr_timespec deadline,
-                                   sigset_t *sig_mask, grpc_error **error) {
-  /* Only g_max_pollers_per_pi threads can be doing polling in parallel.
-     If we cannot get a lease, we cannot continue to do epoll_pwait() */
-  if (!acquire_polling_lease(exec_ctx, worker, pi, deadline, &now)) {
-    return;
-  }
-
-  struct epoll_event ep_ev[GRPC_EPOLL_MAX_EVENTS];
-  int ep_rv;
-  char *err_msg;
-  const char *err_desc = "pollset_work_and_unlock";
-
-  /* timeout_ms is the time between 'now' and 'deadline' */
-  int timeout_ms = poll_deadline_to_millis_timeout(deadline, now);
-
-  GRPC_SCHEDULING_START_BLOCKING_REGION;
-  GRPC_STATS_INC_SYSCALL_POLL(exec_ctx);
-  ep_rv =
-      epoll_pwait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, timeout_ms, sig_mask);
-  GRPC_SCHEDULING_END_BLOCKING_REGION;
-
-  /* Give back the lease right away so that some other thread can enter */
-  release_polling_lease(pi, error);
-
-  if (ep_rv < 0) {
-    if (errno != EINTR) {
-      gpr_asprintf(&err_msg,
-                   "epoll_wait() epoll fd: %d failed with error: %d (%s)",
-                   epoll_fd, errno, strerror(errno));
-      append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-    } else {
-      /* We were interrupted. Save an interation by doing a zero timeout
-         epoll_wait to see if there are any other events of interest */
-      GRPC_POLLING_TRACE("pollset_work: pollset: %p, worker: %p received kick",
-                         (void *)pollset, (void *)worker);
-      ep_rv = epoll_wait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, 0);
-    }
-  }
-
-#ifdef GRPC_TSAN
-  /* See the definition of g_poll_sync for more details */
-  gpr_atm_acq_load(&g_epoll_sync);
-#endif /* defined(GRPC_TSAN) */
-
-  for (int i = 0; i < ep_rv; ++i) {
-    void *data_ptr = ep_ev[i].data.ptr;
-    if (data_ptr == &polling_island_wakeup_fd) {
-      GRPC_POLLING_TRACE(
-          "pollset_work: pollset: %p, worker: %p polling island (epoll_fd: "
-          "%d) got merged",
-          (void *)pollset, (void *)worker, epoll_fd);
-      /* This means that our polling island is merged with a different
-         island. We do not have to do anything here since the subsequent call
-         to the function pollset_work_and_unlock() will pick up the correct
-         epoll_fd */
-    } else {
-      grpc_fd *fd = data_ptr;
-      int cancel = ep_ev[i].events & (EPOLLERR | EPOLLHUP);
-      int read_ev = ep_ev[i].events & (EPOLLIN | EPOLLPRI);
-      int write_ev = ep_ev[i].events & EPOLLOUT;
-      if (read_ev || cancel) {
-        fd_become_readable(exec_ctx, fd, pollset);
-      }
-      if (write_ev || cancel) {
-        fd_become_writable(exec_ctx, fd);
-      }
-    }
-  }
-}
-
-/* Note: sig_mask contains the signal mask to use *during* epoll_wait() */
-static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
-                                    grpc_pollset *pollset,
-                                    grpc_pollset_worker *worker,
-                                    gpr_timespec now, gpr_timespec deadline,
-                                    sigset_t *sig_mask, grpc_error **error) {
-  int epoll_fd = -1;
-  polling_island *pi = NULL;
-  GPR_TIMER_BEGIN("pollset_work_and_unlock", 0);
-
-  /* We need to get the epoll_fd to wait on. The epoll_fd is in inside the
-     latest polling island pointed by pollset->po.pi
-
-     Since epoll_fd is immutable, it is safe to read it without a lock on the
-     polling island. There is however a possibility that the polling island from
-     which we got the epoll_fd, got merged with another island in the meantime.
-     This is okay because in such a case, we will wakeup right-away from
-     epoll_pwait() (because any merge will poison the old polling island's epoll
-     set 'polling_island_wakeup_fd') and then pick up the latest polling_island
-     the next time this function - pollset_work_and_unlock()) is called */
-
-  if (pollset->po.pi == NULL) {
-    pollset->po.pi = polling_island_create(exec_ctx, NULL, error);
-    if (pollset->po.pi == NULL) {
-      GPR_TIMER_END("pollset_work_and_unlock", 0);
-      return; /* Fatal error. Cannot continue */
-    }
-
-    PI_ADD_REF(pollset->po.pi, "ps");
-    GRPC_POLLING_TRACE("pollset_work: pollset: %p created new pi: %p",
-                       (void *)pollset, (void *)pollset->po.pi);
-  }
-
-  pi = polling_island_maybe_get_latest(pollset->po.pi);
-  epoll_fd = pi->epoll_fd;
-
-  /* Update the pollset->po.pi since the island being pointed by
-     pollset->po.pi maybe older than the one pointed by pi) */
-  if (pollset->po.pi != pi) {
-    /* Always do PI_ADD_REF before PI_UNREF because PI_UNREF may cause the
-       polling island to be deleted */
-    PI_ADD_REF(pi, "ps");
-    PI_UNREF(exec_ctx, pollset->po.pi, "ps");
-    pollset->po.pi = pi;
-  }
-
-  /* Add an extra ref so that the island does not get destroyed (which means
-     the epoll_fd won't be closed) while we are are doing an epoll_wait() on the
-     epoll_fd */
-  PI_ADD_REF(pi, "ps_work");
-  gpr_mu_unlock(&pollset->po.mu);
-
-  g_current_thread_polling_island = pi;
-  pollset_do_epoll_pwait(exec_ctx, epoll_fd, pollset, pi, worker, now, deadline,
-                         sig_mask, error);
-  g_current_thread_polling_island = NULL;
-
-  GPR_ASSERT(pi != NULL);
-
-  /* Before leaving, release the extra ref we added to the polling island. It
-     is important to use "pi" here (i.e our old copy of pollset->po.pi
-     that we got before releasing the polling island lock). This is because
-     pollset->po.pi pointer might get udpated in other parts of the
-     code when there is an island merge while we are doing epoll_wait() above */
-  PI_UNREF(exec_ctx, pi, "ps_work");
-
-  GPR_TIMER_END("pollset_work_and_unlock", 0);
-}
-
-/* pollset->po.mu lock must be held by the caller before calling this.
-   The function pollset_work() may temporarily release the lock (pollset->po.mu)
-   during the course of its execution but it will always re-acquire the lock and
-   ensure that it is held by the time the function returns */
-static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                                grpc_pollset_worker **worker_hdl,
-                                gpr_timespec now, gpr_timespec deadline) {
-  GPR_TIMER_BEGIN("pollset_work", 0);
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  grpc_pollset_worker worker;
-  pollset_worker_init(&worker);
-
-  if (worker_hdl) *worker_hdl = &worker;
-
-  gpr_tls_set(&g_current_thread_pollset, (intptr_t)pollset);
-  gpr_tls_set(&g_current_thread_worker, (intptr_t)&worker);
-
-  if (pollset->kicked_without_pollers) {
-    /* If the pollset was kicked without pollers, pretend that the current
-       worker got the kick and skip polling. A kick indicates that there is some
-       work that needs attention like an event on the completion queue or an
-       alarm */
-    GPR_TIMER_MARK("pollset_work.kicked_without_pollers", 0);
-    pollset->kicked_without_pollers = 0;
-  } else if (!pollset->shutting_down) {
-    /* We use the posix-signal with number 'grpc_wakeup_signal' for waking up
-       (i.e 'kicking') a worker in the pollset. A 'kick' is a way to inform the
-       worker that there is some pending work that needs immediate attention
-       (like an event on the completion queue, or a polling island merge that
-       results in a new epoll-fd to wait on) and that the worker should not
-       spend time waiting in epoll_pwait().
-
-       A worker can be kicked anytime from the point it is added to the pollset
-       via push_front_worker() (or push_back_worker()) to the point it is
-       removed via remove_worker().
-       If the worker is kicked before/during it calls epoll_pwait(), it should
-       immediately exit from epoll_wait(). If the worker is kicked after it
-       returns from epoll_wait(), then nothing really needs to be done.
-
-       To accomplish this, we mask 'grpc_wakeup_signal' on this thread at all
-       times *except* when it is in epoll_pwait(). This way, the worker never
-       misses acting on a kick */
-
-    if (!g_initialized_sigmask) {
-      sigemptyset(&g_wakeup_sig_set);
-      sigaddset(&g_wakeup_sig_set, grpc_wakeup_signal);
-      pthread_sigmask(SIG_BLOCK, &g_wakeup_sig_set, &g_orig_sigmask);
-      sigdelset(&g_orig_sigmask, grpc_wakeup_signal);
-      g_initialized_sigmask = true;
-      /* new_mask:       The new thread mask which blocks 'grpc_wakeup_signal'.
-                         This is the mask used at all times *except during
-                         epoll_wait()*"
-         g_orig_sigmask: The thread mask which allows 'grpc_wakeup_signal' and
-                         this is the mask to use *during epoll_wait()*
-
-         The new_mask is set on the worker before it is added to the pollset
-         (i.e before it can be kicked) */
-    }
-
-    push_front_worker(pollset, &worker); /* Add worker to pollset */
-
-    pollset_work_and_unlock(exec_ctx, pollset, &worker, now, deadline,
-                            &g_orig_sigmask, &error);
-    grpc_exec_ctx_flush(exec_ctx);
-
-    gpr_mu_lock(&pollset->po.mu);
-
-    /* Note: There is no need to reset worker.is_kicked to 0 since we are no
-       longer going to use this worker */
-    remove_worker(pollset, &worker);
-  }
-
-  /* If we are the last worker on the pollset (i.e pollset_has_workers() is
-     false at this point) and the pollset is shutting down, we may have to
-     finish the shutdown process by calling finish_shutdown_locked().
-     See pollset_shutdown() for more details.
-
-     Note: Continuing to access pollset here is safe; it is the caller's
-     responsibility to not destroy a pollset when it has outstanding calls to
-     pollset_work() */
-  if (pollset->shutting_down && !pollset_has_workers(pollset) &&
-      !pollset->finish_shutdown_called) {
-    GPR_TIMER_MARK("pollset_work.finish_shutdown_locked", 0);
-    finish_shutdown_locked(exec_ctx, pollset);
-
-    gpr_mu_unlock(&pollset->po.mu);
-    grpc_exec_ctx_flush(exec_ctx);
-    gpr_mu_lock(&pollset->po.mu);
-  }
-
-  if (worker_hdl) *worker_hdl = NULL;
-
-  gpr_tls_set(&g_current_thread_pollset, (intptr_t)0);
-  gpr_tls_set(&g_current_thread_worker, (intptr_t)0);
-
-  GPR_TIMER_END("pollset_work", 0);
-
-  GRPC_LOG_IF_ERROR("pollset_work", GRPC_ERROR_REF(error));
-  return error;
-}
-
-static void add_poll_object(grpc_exec_ctx *exec_ctx, poll_obj *bag,
-                            poll_obj_type bag_type, poll_obj *item,
-                            poll_obj_type item_type) {
-  GPR_TIMER_BEGIN("add_poll_object", 0);
-
-#ifndef NDEBUG
-  GPR_ASSERT(item->obj_type == item_type);
-  GPR_ASSERT(bag->obj_type == bag_type);
-#endif
-
-  grpc_error *error = GRPC_ERROR_NONE;
-  polling_island *pi_new = NULL;
-
-  gpr_mu_lock(&bag->mu);
-  gpr_mu_lock(&item->mu);
-
-retry:
-  /*
-   * 1) If item->pi and bag->pi are both non-NULL and equal, do nothing
-   * 2) If item->pi and bag->pi are both NULL, create a new polling island (with
-   *    a refcount of 2) and point item->pi and bag->pi to the new island
-   * 3) If exactly one of item->pi or bag->pi is NULL, update it to point to
-   *    the other's non-NULL pi
-   * 4) Finally if item->pi and bag-pi are non-NULL and not-equal, merge the
-   *    polling islands and update item->pi and bag->pi to point to the new
-   *    island
-   */
-
-  /* Early out if we are trying to add an 'fd' to a 'bag' but the fd is already
-   * orphaned */
-  if (item_type == POLL_OBJ_FD && (FD_FROM_PO(item))->orphaned) {
-    gpr_mu_unlock(&item->mu);
-    gpr_mu_unlock(&bag->mu);
-    return;
-  }
-
-  if (item->pi == bag->pi) {
-    pi_new = item->pi;
-    if (pi_new == NULL) {
-      /* GPR_ASSERT(item->pi == bag->pi == NULL) */
-
-      /* If we are adding an fd to a bag (i.e pollset or pollset_set), then
-       * we need to do some extra work to make TSAN happy */
-      if (item_type == POLL_OBJ_FD) {
-        /* Unlock before creating a new polling island: the polling island will
-           create a workqueue which creates a file descriptor, and holding an fd
-           lock here can eventually cause a loop to appear to TSAN (making it
-           unhappy). We don't think it's a real loop (there's an epoch point
-           where that loop possibility disappears), but the advantages of
-           keeping TSAN happy outweigh any performance advantage we might have
-           by keeping the lock held. */
-        gpr_mu_unlock(&item->mu);
-        pi_new = polling_island_create(exec_ctx, FD_FROM_PO(item), &error);
-        gpr_mu_lock(&item->mu);
-
-        /* Need to reverify any assumptions made between the initial lock and
-           getting to this branch: if they've changed, we need to throw away our
-           work and figure things out again. */
-        if (item->pi != NULL) {
-          GRPC_POLLING_TRACE(
-              "add_poll_object: Raced creating new polling island. pi_new: %p "
-              "(fd: %d, %s: %p)",
-              (void *)pi_new, FD_FROM_PO(item)->fd, poll_obj_string(bag_type),
-              (void *)bag);
-          /* No need to lock 'pi_new' here since this is a new polling island
-             and no one has a reference to it yet */
-          polling_island_remove_all_fds_locked(pi_new, true, &error);
-
-          /* Ref and unref so that the polling island gets deleted during unref
-           */
-          PI_ADD_REF(pi_new, "dance_of_destruction");
-          PI_UNREF(exec_ctx, pi_new, "dance_of_destruction");
-          goto retry;
-        }
-      } else {
-        pi_new = polling_island_create(exec_ctx, NULL, &error);
-      }
-
-      GRPC_POLLING_TRACE(
-          "add_poll_object: Created new polling island. pi_new: %p (%s: %p, "
-          "%s: %p)",
-          (void *)pi_new, poll_obj_string(item_type), (void *)item,
-          poll_obj_string(bag_type), (void *)bag);
-    } else {
-      GRPC_POLLING_TRACE(
-          "add_poll_object: Same polling island. pi: %p (%s, %s)",
-          (void *)pi_new, poll_obj_string(item_type),
-          poll_obj_string(bag_type));
-    }
-  } else if (item->pi == NULL) {
-    /* GPR_ASSERT(bag->pi != NULL) */
-    /* Make pi_new point to latest pi*/
-    pi_new = polling_island_lock(bag->pi);
-
-    if (item_type == POLL_OBJ_FD) {
-      grpc_fd *fd = FD_FROM_PO(item);
-      polling_island_add_fds_locked(pi_new, &fd, 1, true, &error);
-    }
-
-    gpr_mu_unlock(&pi_new->mu);
-    GRPC_POLLING_TRACE(
-        "add_poll_obj: item->pi was NULL. pi_new: %p (item(%s): %p, "
-        "bag(%s): %p)",
-        (void *)pi_new, poll_obj_string(item_type), (void *)item,
-        poll_obj_string(bag_type), (void *)bag);
-  } else if (bag->pi == NULL) {
-    /* GPR_ASSERT(item->pi != NULL) */
-    /* Make pi_new to point to latest pi */
-    pi_new = polling_island_lock(item->pi);
-    gpr_mu_unlock(&pi_new->mu);
-    GRPC_POLLING_TRACE(
-        "add_poll_obj: bag->pi was NULL. pi_new: %p (item(%s): %p, "
-        "bag(%s): %p)",
-        (void *)pi_new, poll_obj_string(item_type), (void *)item,
-        poll_obj_string(bag_type), (void *)bag);
-  } else {
-    pi_new = polling_island_merge(item->pi, bag->pi, &error);
-    GRPC_POLLING_TRACE(
-        "add_poll_obj: polling islands merged. pi_new: %p (item(%s): %p, "
-        "bag(%s): %p)",
-        (void *)pi_new, poll_obj_string(item_type), (void *)item,
-        poll_obj_string(bag_type), (void *)bag);
-  }
-
-  /* At this point, pi_new is the polling island that both item->pi and bag->pi
-     MUST be pointing to */
-
-  if (item->pi != pi_new) {
-    PI_ADD_REF(pi_new, poll_obj_string(item_type));
-    if (item->pi != NULL) {
-      PI_UNREF(exec_ctx, item->pi, poll_obj_string(item_type));
-    }
-    item->pi = pi_new;
-  }
-
-  if (bag->pi != pi_new) {
-    PI_ADD_REF(pi_new, poll_obj_string(bag_type));
-    if (bag->pi != NULL) {
-      PI_UNREF(exec_ctx, bag->pi, poll_obj_string(bag_type));
-    }
-    bag->pi = pi_new;
-  }
-
-  gpr_mu_unlock(&item->mu);
-  gpr_mu_unlock(&bag->mu);
-
-  GRPC_LOG_IF_ERROR("add_poll_object", error);
-  GPR_TIMER_END("add_poll_object", 0);
-}
-
-static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                           grpc_fd *fd) {
-  add_poll_object(exec_ctx, &pollset->po, POLL_OBJ_POLLSET, &fd->po,
-                  POLL_OBJ_FD);
-}
-
-/*******************************************************************************
- * Pollset-set Definitions
- */
-
-static grpc_pollset_set *pollset_set_create(void) {
-  grpc_pollset_set *pss = gpr_malloc(sizeof(*pss));
-  gpr_mu_init(&pss->po.mu);
-  pss->po.pi = NULL;
-#ifndef NDEBUG
-  pss->po.obj_type = POLL_OBJ_POLLSET_SET;
-#endif
-  return pss;
-}
-
-static void pollset_set_destroy(grpc_exec_ctx *exec_ctx,
-                                grpc_pollset_set *pss) {
-  gpr_mu_destroy(&pss->po.mu);
-
-  if (pss->po.pi != NULL) {
-    PI_UNREF(exec_ctx, pss->po.pi, "pss_destroy");
-  }
-
-  gpr_free(pss);
-}
-
-static void pollset_set_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset_set *pss,
-                               grpc_fd *fd) {
-  add_poll_object(exec_ctx, &pss->po, POLL_OBJ_POLLSET_SET, &fd->po,
-                  POLL_OBJ_FD);
-}
-
-static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx, grpc_pollset_set *pss,
-                               grpc_fd *fd) {
-  /* Nothing to do */
-}
-
-static void pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
-                                    grpc_pollset_set *pss, grpc_pollset *ps) {
-  add_poll_object(exec_ctx, &pss->po, POLL_OBJ_POLLSET_SET, &ps->po,
-                  POLL_OBJ_POLLSET);
-}
-
-static void pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
-                                    grpc_pollset_set *pss, grpc_pollset *ps) {
-  /* Nothing to do */
-}
-
-static void pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
-                                        grpc_pollset_set *bag,
-                                        grpc_pollset_set *item) {
-  add_poll_object(exec_ctx, &bag->po, POLL_OBJ_POLLSET_SET, &item->po,
-                  POLL_OBJ_POLLSET_SET);
-}
-
-static void pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
-                                        grpc_pollset_set *bag,
-                                        grpc_pollset_set *item) {
-  /* Nothing to do */
-}
-
-/*******************************************************************************
- * Event engine binding
- */
-
-static void shutdown_engine(void) {
-  fd_global_shutdown();
-  pollset_global_shutdown();
-  polling_island_global_shutdown();
-}
-
-static const grpc_event_engine_vtable vtable = {
-    .pollset_size = sizeof(grpc_pollset),
-
-    .fd_create = fd_create,
-    .fd_wrapped_fd = fd_wrapped_fd,
-    .fd_orphan = fd_orphan,
-    .fd_shutdown = fd_shutdown,
-    .fd_is_shutdown = fd_is_shutdown,
-    .fd_notify_on_read = fd_notify_on_read,
-    .fd_notify_on_write = fd_notify_on_write,
-    .fd_get_read_notifier_pollset = fd_get_read_notifier_pollset,
-
-    .pollset_init = pollset_init,
-    .pollset_shutdown = pollset_shutdown,
-    .pollset_destroy = pollset_destroy,
-    .pollset_work = pollset_work,
-    .pollset_kick = pollset_kick,
-    .pollset_add_fd = pollset_add_fd,
-
-    .pollset_set_create = pollset_set_create,
-    .pollset_set_destroy = pollset_set_destroy,
-    .pollset_set_add_pollset = pollset_set_add_pollset,
-    .pollset_set_del_pollset = pollset_set_del_pollset,
-    .pollset_set_add_pollset_set = pollset_set_add_pollset_set,
-    .pollset_set_del_pollset_set = pollset_set_del_pollset_set,
-    .pollset_set_add_fd = pollset_set_add_fd,
-    .pollset_set_del_fd = pollset_set_del_fd,
-
-    .shutdown_engine = shutdown_engine,
-};
-
-/* It is possible that GLIBC has epoll but the underlying kernel doesn't.
- * Create a dummy epoll_fd to make sure epoll support is available */
-static bool is_epoll_available() {
-  int fd = epoll_create1(EPOLL_CLOEXEC);
-  if (fd < 0) {
-    gpr_log(
-        GPR_ERROR,
-        "epoll_create1 failed with error: %d. Not using epoll polling engine",
-        fd);
-    return false;
-  }
-  close(fd);
-  return true;
-}
-
-/* This is mainly for testing purposes. Checks to see if environment variable
- * GRPC_MAX_POLLERS_PER_PI is set and if so, assigns that value to
- * g_max_pollers_per_pi (any negative value is considered INT_MAX) */
-static void set_max_pollers_per_island() {
-  char *s = gpr_getenv("GRPC_MAX_POLLERS_PER_PI");
-  if (s) {
-    g_max_pollers_per_pi = (int)strtol(s, NULL, 10);
-    if (g_max_pollers_per_pi < 0) {
-      g_max_pollers_per_pi = INT_MAX;
-    }
-  } else {
-    g_max_pollers_per_pi = INT_MAX;
-  }
-
-  gpr_log(GPR_INFO, "Max number of pollers per polling island: %d",
-          g_max_pollers_per_pi);
-}
-
-const grpc_event_engine_vtable *grpc_init_epoll_limited_pollers_linux(
-    bool explicitly_requested) {
-  if (!explicitly_requested) {
-    return NULL;
-  }
-
-  /* If use of signals is disabled, we cannot use epoll engine*/
-  if (is_grpc_wakeup_signal_initialized && grpc_wakeup_signal < 0) {
-    return NULL;
-  }
-
-  if (!grpc_has_wakeup_fd()) {
-    return NULL;
-  }
-
-  if (!is_epoll_available()) {
-    return NULL;
-  }
-
-  if (!is_grpc_wakeup_signal_initialized) {
-    grpc_use_signal(SIGRTMIN + 6);
-  }
-
-  set_max_pollers_per_island();
-
-  fd_global_init();
-
-  if (!GRPC_LOG_IF_ERROR("pollset_global_init", pollset_global_init())) {
-    return NULL;
-  }
-
-  if (!GRPC_LOG_IF_ERROR("polling_island_global_init",
-                         polling_island_global_init())) {
-    return NULL;
-  }
-
-  return &vtable;
-}
-
-#else /* defined(GRPC_LINUX_EPOLL) */
-#if defined(GRPC_POSIX_SOCKET)
-#include "src/core/lib/iomgr/ev_posix.h"
-/* If GRPC_LINUX_EPOLL is not defined, it means epoll is not available. Return
- * NULL */
-const grpc_event_engine_vtable *grpc_init_epoll_limited_pollers_linux(
-    bool explicitly_requested) {
-  return NULL;
-}
-#endif /* defined(GRPC_POSIX_SOCKET) */
-#endif /* !defined(GRPC_LINUX_EPOLL) */
diff --git a/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.h b/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.h
deleted file mode 100644
index 1d6af5f52c..0000000000
--- a/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/*
- *
- * Copyright 2015 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#ifndef GRPC_CORE_LIB_IOMGR_EV_EPOLL_LIMITED_POLLERS_LINUX_H
-#define GRPC_CORE_LIB_IOMGR_EV_EPOLL_LIMITED_POLLERS_LINUX_H
-
-#include "src/core/lib/iomgr/ev_posix.h"
-#include "src/core/lib/iomgr/port.h"
-
-const grpc_event_engine_vtable *grpc_init_epoll_limited_pollers_linux(
-    bool explicitly_requested);
-
-#endif /* GRPC_CORE_LIB_IOMGR_EV_EPOLL_LIMITED_POLLERS_LINUX_H */
diff --git a/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c b/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c
deleted file mode 100644
index ddb8c74d2d..0000000000
--- a/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c
+++ /dev/null
@@ -1,1184 +0,0 @@
-/*
- *
- * Copyright 2017 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#include "src/core/lib/iomgr/port.h"
-
-/* This polling engine is only relevant on linux kernels supporting epoll() */
-#ifdef GRPC_LINUX_EPOLL
-
-#include "src/core/lib/iomgr/ev_epoll_thread_pool_linux.h"
-
-#include <assert.h>
-#include <errno.h>
-#include <limits.h>
-#include <poll.h>
-#include <pthread.h>
-#include <string.h>
-#include <sys/epoll.h>
-#include <sys/socket.h>
-#include <unistd.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/cpu.h>
-#include <grpc/support/log.h>
-#include <grpc/support/string_util.h>
-#include <grpc/support/thd.h>
-#include <grpc/support/tls.h>
-#include <grpc/support/useful.h>
-
-#include "src/core/lib/debug/stats.h"
-#include "src/core/lib/iomgr/ev_posix.h"
-#include "src/core/lib/iomgr/iomgr_internal.h"
-#include "src/core/lib/iomgr/lockfree_event.h"
-#include "src/core/lib/iomgr/timer.h"
-#include "src/core/lib/iomgr/wakeup_fd_posix.h"
-#include "src/core/lib/profiling/timers.h"
-#include "src/core/lib/support/block_annotate.h"
-
-/* TODO: sreek - Move this to init.c and initialize this like other tracers. */
-#define GRPC_POLLING_TRACE(fmt, ...)        \
-  if (GRPC_TRACER_ON(grpc_polling_trace)) { \
-    gpr_log(GPR_INFO, (fmt), __VA_ARGS__);  \
-  }
-
-/* The alarm system needs to be able to wakeup 'some poller' sometimes
- * (specifically when a new alarm needs to be triggered earlier than the next
- * alarm 'epoch'). This wakeup_fd gives us something to alert on when such a
- * case occurs. */
-
-struct epoll_set;
-
-#define GRPC_POLLSET_KICK_BROADCAST ((grpc_pollset_worker *)1)
-
-/*******************************************************************************
- * Fd Declarations
- */
-struct grpc_fd {
-  gpr_mu mu;
-  struct epoll_set *eps;
-
-  int fd;
-
-  /* The fd is either closed or we relinquished control of it. In either cases,
-     this indicates that the 'fd' on this structure is no longer valid */
-  bool orphaned;
-
-  gpr_atm read_closure;
-  gpr_atm write_closure;
-
-  struct grpc_fd *freelist_next;
-  grpc_closure *on_done_closure;
-
-  grpc_iomgr_object iomgr_object;
-};
-
-static void fd_global_init(void);
-static void fd_global_shutdown(void);
-
-/*******************************************************************************
- * epoll set Declarations
- */
-
-#ifndef NDEBUG
-
-#define EPS_ADD_REF(p, r) eps_add_ref_dbg((p), (r), __FILE__, __LINE__)
-#define EPS_UNREF(exec_ctx, p, r) \
-  eps_unref_dbg((exec_ctx), (p), (r), __FILE__, __LINE__)
-
-#else
-
-#define EPS_ADD_REF(p, r) eps_add_ref((p))
-#define EPS_UNREF(exec_ctx, p, r) eps_unref((exec_ctx), (p))
-
-#endif
-
-typedef struct epoll_set {
-  /* Mutex poller should acquire to poll this. This enforces that only one
-   * poller can be polling on epoll_set at any time */
-  gpr_mu mu;
-
-  /* Ref count. Use EPS_ADD_REF() and EPS_UNREF() macros to increment/decrement
-     the refcount. Once the ref count becomes zero, this structure is destroyed
-     which means we should ensure that there is never a scenario where a
-     EPS_ADD_REF() is racing with a EPS_UNREF() that just made the ref_count
-     zero. */
-  gpr_atm ref_count;
-
-  /* Number of threads currently polling on this epoll set*/
-  gpr_atm poller_count;
-
-  /* Is the epoll set shutdown */
-  gpr_atm is_shutdown;
-
-  /* The fd of the underlying epoll set */
-  int epoll_fd;
-} epoll_set;
-
-/*******************************************************************************
- * Pollset Declarations
- */
-struct grpc_pollset_worker {
-  gpr_cv kick_cv;
-
-  struct grpc_pollset_worker *next;
-  struct grpc_pollset_worker *prev;
-};
-
-struct grpc_pollset {
-  gpr_mu mu;
-  struct epoll_set *eps;
-
-  grpc_pollset_worker root_worker;
-  bool kicked_without_pollers;
-
-  bool shutting_down;          /* Is the pollset shutting down ? */
-  bool finish_shutdown_called; /* Is the 'finish_shutdown_locked()' called ? */
-  grpc_closure *shutdown_done; /* Called after after shutdown is complete */
-};
-
-/*******************************************************************************
- * Pollset-set Declarations
- */
-struct grpc_pollset_set {
-  char unused;
-};
-
-/*****************************************************************************
- * Dedicated polling threads and pollsets - Declarations
- */
-
-size_t g_num_eps = 1;
-struct epoll_set **g_epoll_sets = NULL;
-gpr_atm g_next_eps;
-size_t g_num_threads_per_eps = 1;
-gpr_thd_id *g_poller_threads = NULL;
-
-/* Used as read-notifier pollsets for fds. We won't be using read notifier
- * pollsets with this polling engine. So it does not matter what pollset we
- * return */
-grpc_pollset g_read_notifier;
-
-static void add_fd_to_eps(grpc_fd *fd);
-static bool init_epoll_sets();
-static void shutdown_epoll_sets();
-static void poller_thread_loop(void *arg);
-static void start_poller_threads();
-static void shutdown_poller_threads();
-
-/*******************************************************************************
- * Common helpers
- */
-
-static bool append_error(grpc_error **composite, grpc_error *error,
-                         const char *desc) {
-  if (error == GRPC_ERROR_NONE) return true;
-  if (*composite == GRPC_ERROR_NONE) {
-    *composite = GRPC_ERROR_CREATE_FROM_COPIED_STRING(desc);
-  }
-  *composite = grpc_error_add_child(*composite, error);
-  return false;
-}
-
-/*******************************************************************************
- * epoll set Definitions
- */
-
-/* The wakeup fd that is used to wake up all threads in an epoll_set informing
-   that the epoll set is shutdown.  This wakeup fd initialized to be readable
-   and MUST NOT be consumed i.e the threads that woke up MUST NOT call
-   grpc_wakeup_fd_consume_wakeup() */
-static grpc_wakeup_fd epoll_set_wakeup_fd;
-
-/* The epoll set being polled right now.
-   See comments in workqueue_maybe_wakeup for why this is tracked. */
-static __thread epoll_set *g_current_thread_epoll_set;
-
-/* Forward declaration */
-static void epoll_set_delete(epoll_set *eps);
-
-#ifdef GRPC_TSAN
-/* Currently TSAN may incorrectly flag data races between epoll_ctl and
-   epoll_wait for any grpc_fd structs that are added to the epoll set via
-   epoll_ctl and are returned (within a very short window) via epoll_wait().
-
-   To work-around this race, we establish a happens-before relation between
-   the code just-before epoll_ctl() and the code after epoll_wait() by using
-   this atomic */
-gpr_atm g_epoll_sync;
-#endif /* defined(GRPC_TSAN) */
-
-static void eps_add_ref(epoll_set *eps);
-static void eps_unref(grpc_exec_ctx *exec_ctx, epoll_set *eps);
-
-#ifndef NDEBUG
-static void eps_add_ref_dbg(epoll_set *eps, const char *reason,
-                            const char *file, int line) {
-  if (GRPC_TRACER_ON(grpc_polling_trace)) {
-    gpr_atm old_cnt = gpr_atm_acq_load(&eps->ref_count);
-    gpr_log(GPR_DEBUG, "Add ref eps: %p, old:%" PRIdPTR " -> new:%" PRIdPTR
-                       " (%s) - (%s, %d)",
-            eps, old_cnt, old_cnt + 1, reason, file, line);
-  }
-  eps_add_ref(eps);
-}
-
-static void eps_unref_dbg(grpc_exec_ctx *exec_ctx, epoll_set *eps,
-                          const char *reason, const char *file, int line) {
-  if (GRPC_TRACER_ON(grpc_polling_trace)) {
-    gpr_atm old_cnt = gpr_atm_acq_load(&eps->ref_count);
-    gpr_log(GPR_DEBUG, "Unref eps: %p, old:%" PRIdPTR " -> new:%" PRIdPTR
-                       " (%s) - (%s, %d)",
-            eps, old_cnt, (old_cnt - 1), reason, file, line);
-  }
-  eps_unref(exec_ctx, eps);
-}
-#endif
-
-static void eps_add_ref(epoll_set *eps) {
-  gpr_atm_no_barrier_fetch_add(&eps->ref_count, 1);
-}
-
-static void eps_unref(grpc_exec_ctx *exec_ctx, epoll_set *eps) {
-  /* If ref count went to zero, delete the epoll set. This deletion is
-     not done under a lock since once the ref count goes to zero, we are
-     guaranteed that no one else holds a reference to the epoll set (and
-     that there is no racing eps_add_ref() call either).*/
-  if (1 == gpr_atm_full_fetch_add(&eps->ref_count, -1)) {
-    epoll_set_delete(eps);
-  }
-}
-
-static void epoll_set_add_fd_locked(epoll_set *eps, grpc_fd *fd,
-                                    grpc_error **error) {
-  int err;
-  struct epoll_event ev;
-  char *err_msg;
-  const char *err_desc = "epoll_set_add_fd_locked";
-
-#ifdef GRPC_TSAN
-  /* See the definition of g_epoll_sync for more context */
-  gpr_atm_rel_store(&g_epoll_sync, (gpr_atm)0);
-#endif /* defined(GRPC_TSAN) */
-
-  ev.events = (uint32_t)(EPOLLIN | EPOLLOUT | EPOLLET);
-  ev.data.ptr = fd;
-  err = epoll_ctl(eps->epoll_fd, EPOLL_CTL_ADD, fd->fd, &ev);
-  if (err < 0 && errno != EEXIST) {
-    gpr_asprintf(
-        &err_msg,
-        "epoll_ctl (epoll_fd: %d) add fd: %d failed with error: %d (%s)",
-        eps->epoll_fd, fd->fd, errno, strerror(errno));
-    append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-    gpr_free(err_msg);
-  }
-}
-
-static void epoll_set_add_wakeup_fd_locked(epoll_set *eps,
-                                           grpc_wakeup_fd *wakeup_fd,
-                                           grpc_error **error) {
-  struct epoll_event ev;
-  int err;
-  char *err_msg;
-  const char *err_desc = "epoll_set_add_wakeup_fd";
-
-  ev.events = (uint32_t)(EPOLLIN | EPOLLET);
-  ev.data.ptr = wakeup_fd;
-  err = epoll_ctl(eps->epoll_fd, EPOLL_CTL_ADD,
-                  GRPC_WAKEUP_FD_GET_READ_FD(wakeup_fd), &ev);
-  if (err < 0 && errno != EEXIST) {
-    gpr_asprintf(&err_msg,
-                 "epoll_ctl (epoll_fd: %d) add wakeup fd: %d failed with "
-                 "error: %d (%s)",
-                 eps->epoll_fd, GRPC_WAKEUP_FD_GET_READ_FD(wakeup_fd), errno,
-                 strerror(errno));
-    append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-    gpr_free(err_msg);
-  }
-}
-
-static void epoll_set_remove_fd(epoll_set *eps, grpc_fd *fd, bool is_fd_closed,
-                                grpc_error **error) {
-  int err;
-  char *err_msg;
-  const char *err_desc = "epoll_set_remove_fd";
-
-  /* If fd is already closed, then it would have been automatically been removed
-     from the epoll set */
-  if (!is_fd_closed) {
-    err = epoll_ctl(eps->epoll_fd, EPOLL_CTL_DEL, fd->fd, NULL);
-    if (err < 0 && errno != ENOENT) {
-      gpr_asprintf(
-          &err_msg,
-          "epoll_ctl (epoll_fd: %d) del fd: %d failed with error: %d (%s)",
-          eps->epoll_fd, fd->fd, errno, strerror(errno));
-      append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-      gpr_free(err_msg);
-    }
-  }
-}
-
-/* Might return NULL in case of an error */
-static epoll_set *epoll_set_create(grpc_error **error) {
-  epoll_set *eps = NULL;
-  const char *err_desc = "epoll_set_create";
-
-  *error = GRPC_ERROR_NONE;
-
-  eps = gpr_malloc(sizeof(*eps));
-  eps->epoll_fd = -1;
-
-  gpr_mu_init(&eps->mu);
-
-  gpr_atm_rel_store(&eps->ref_count, 0);
-  gpr_atm_rel_store(&eps->poller_count, 0);
-
-  gpr_atm_rel_store(&eps->is_shutdown, false);
-
-  eps->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
-
-  if (eps->epoll_fd < 0) {
-    append_error(error, GRPC_OS_ERROR(errno, "epoll_create1"), err_desc);
-    goto done;
-  }
-
-done:
-  if (*error != GRPC_ERROR_NONE) {
-    epoll_set_delete(eps);
-    eps = NULL;
-  }
-  return eps;
-}
-
-static void epoll_set_delete(epoll_set *eps) {
-  if (eps->epoll_fd >= 0) {
-    close(eps->epoll_fd);
-  }
-
-  gpr_mu_destroy(&eps->mu);
-
-  gpr_free(eps);
-}
-
-static grpc_error *epoll_set_global_init() {
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  error = grpc_wakeup_fd_init(&epoll_set_wakeup_fd);
-  if (error == GRPC_ERROR_NONE) {
-    error = grpc_wakeup_fd_wakeup(&epoll_set_wakeup_fd);
-  }
-
-  return error;
-}
-
-static void epoll_set_global_shutdown() {
-  grpc_wakeup_fd_destroy(&epoll_set_wakeup_fd);
-}
-
-/*******************************************************************************
- * Fd Definitions
- */
-
-/* We need to keep a freelist not because of any concerns of malloc performance
- * but instead so that implementations with multiple threads in (for example)
- * epoll_wait deal with the race between pollset removal and incoming poll
- * notifications.
- *
- * The problem is that the poller ultimately holds a reference to this
- * object, so it is very difficult to know when is safe to free it, at least
- * without some expensive synchronization.
- *
- * If we keep the object freelisted, in the worst case losing this race just
- * becomes a spurious read notification on a reused fd.
- */
-
-static grpc_fd *fd_freelist = NULL;
-static gpr_mu fd_freelist_mu;
-
-static grpc_fd *get_fd_from_freelist() {
-  grpc_fd *new_fd = NULL;
-
-  gpr_mu_lock(&fd_freelist_mu);
-  if (fd_freelist != NULL) {
-    new_fd = fd_freelist;
-    fd_freelist = fd_freelist->freelist_next;
-  }
-  gpr_mu_unlock(&fd_freelist_mu);
-  return new_fd;
-}
-
-static void add_fd_to_freelist(grpc_fd *fd) {
-  gpr_mu_lock(&fd_freelist_mu);
-  fd->freelist_next = fd_freelist;
-  fd_freelist = fd;
-  grpc_iomgr_unregister_object(&fd->iomgr_object);
-
-  grpc_lfev_destroy(&fd->read_closure);
-  grpc_lfev_destroy(&fd->write_closure);
-
-  gpr_mu_unlock(&fd_freelist_mu);
-}
-
-static void fd_global_init(void) { gpr_mu_init(&fd_freelist_mu); }
-
-static void fd_global_shutdown(void) {
-  gpr_mu_lock(&fd_freelist_mu);
-  gpr_mu_unlock(&fd_freelist_mu);
-  while (fd_freelist != NULL) {
-    grpc_fd *fd = fd_freelist;
-    fd_freelist = fd_freelist->freelist_next;
-    gpr_mu_destroy(&fd->mu);
-    gpr_free(fd);
-  }
-  gpr_mu_destroy(&fd_freelist_mu);
-}
-
-static grpc_fd *fd_create(int fd, const char *name) {
-  grpc_fd *new_fd = get_fd_from_freelist();
-  if (new_fd == NULL) {
-    new_fd = gpr_malloc(sizeof(grpc_fd));
-    gpr_mu_init(&new_fd->mu);
-  }
-
-  /* Note: It is not really needed to get the new_fd->mu lock here. If this
-   * is a newly created fd (or an fd we got from the freelist), no one else
-   * would be holding a lock to it anyway. */
-  gpr_mu_lock(&new_fd->mu);
-  new_fd->eps = NULL;
-
-  new_fd->fd = fd;
-  new_fd->orphaned = false;
-  grpc_lfev_init(&new_fd->read_closure);
-  grpc_lfev_init(&new_fd->write_closure);
-
-  new_fd->freelist_next = NULL;
-  new_fd->on_done_closure = NULL;
-
-  gpr_mu_unlock(&new_fd->mu);
-
-  char *fd_name;
-  gpr_asprintf(&fd_name, "%s fd=%d", name, fd);
-  grpc_iomgr_register_object(&new_fd->iomgr_object, fd_name);
-  gpr_log(GPR_DEBUG, "FD %d %p create %s", fd, (void *)new_fd, fd_name);
-  gpr_free(fd_name);
-
-  /* Associate the fd with one of the eps */
-  add_fd_to_eps(new_fd);
-  return new_fd;
-}
-
-static int fd_wrapped_fd(grpc_fd *fd) {
-  int ret_fd = -1;
-  gpr_mu_lock(&fd->mu);
-  if (!fd->orphaned) {
-    ret_fd = fd->fd;
-  }
-  gpr_mu_unlock(&fd->mu);
-
-  return ret_fd;
-}
-
-static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                      grpc_closure *on_done, int *release_fd,
-                      bool already_closed, const char *reason) {
-  bool is_fd_closed = already_closed;
-  grpc_error *error = GRPC_ERROR_NONE;
-  epoll_set *unref_eps = NULL;
-
-  gpr_mu_lock(&fd->mu);
-  fd->on_done_closure = on_done;
-
-  /* If release_fd is not NULL, we should be relinquishing control of the file
-     descriptor fd->fd (but we still own the grpc_fd structure). */
-  if (release_fd != NULL) {
-    *release_fd = fd->fd;
-  } else if (!is_fd_closed) {
-    close(fd->fd);
-    is_fd_closed = true;
-  }
-
-  fd->orphaned = true;
-
-  /* Remove the fd from the epoll set */
-  if (fd->eps != NULL) {
-    epoll_set_remove_fd(fd->eps, fd, is_fd_closed, &error);
-    unref_eps = fd->eps;
-    fd->eps = NULL;
-  }
-
-  GRPC_CLOSURE_SCHED(exec_ctx, fd->on_done_closure, GRPC_ERROR_REF(error));
-
-  gpr_mu_unlock(&fd->mu);
-
-  /* We are done with this fd. Release it (i.e add back to freelist) */
-  add_fd_to_freelist(fd);
-
-  if (unref_eps != NULL) {
-    /* Unref stale epoll set here, outside the fd lock above.
-       The epoll set owns a workqueue which owns an fd, and unreffing
-       inside the lock can cause an eventual lock loop that makes TSAN very
-       unhappy. */
-    EPS_UNREF(exec_ctx, unref_eps, "fd_orphan");
-  }
-  GRPC_LOG_IF_ERROR("fd_orphan", GRPC_ERROR_REF(error));
-  GRPC_ERROR_UNREF(error);
-}
-
-/* This polling engine doesn't really need the read notifier functionality. So
- * it just returns a dummy read notifier pollset */
-static grpc_pollset *fd_get_read_notifier_pollset(grpc_exec_ctx *exec_ctx,
-                                                  grpc_fd *fd) {
-  return &g_read_notifier;
-}
-
-static bool fd_is_shutdown(grpc_fd *fd) {
-  return grpc_lfev_is_shutdown(&fd->read_closure);
-}
-
-/* Might be called multiple times */
-static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_error *why) {
-  if (grpc_lfev_set_shutdown(exec_ctx, &fd->read_closure,
-                             GRPC_ERROR_REF(why))) {
-    shutdown(fd->fd, SHUT_RDWR);
-    grpc_lfev_set_shutdown(exec_ctx, &fd->write_closure, GRPC_ERROR_REF(why));
-  }
-  GRPC_ERROR_UNREF(why);
-}
-
-static void fd_notify_on_read(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                              grpc_closure *closure) {
-  grpc_lfev_notify_on(exec_ctx, &fd->read_closure, closure, "read");
-}
-
-static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
-                               grpc_closure *closure) {
-  grpc_lfev_notify_on(exec_ctx, &fd->write_closure, closure, "write");
-}
-
-/*******************************************************************************
- * Pollset Definitions
- */
-/* TODO: sreek - Not needed anymore */
-GPR_TLS_DECL(g_current_thread_pollset);
-GPR_TLS_DECL(g_current_thread_worker);
-
-static void pollset_worker_init(grpc_pollset_worker *worker) {
-  worker->next = worker->prev = NULL;
-  gpr_cv_init(&worker->kick_cv);
-}
-
-/* Global state management */
-static grpc_error *pollset_global_init(void) {
-  gpr_tls_init(&g_current_thread_pollset);
-  gpr_tls_init(&g_current_thread_worker);
-  return GRPC_ERROR_NONE;
-}
-
-static void pollset_global_shutdown(void) {
-  gpr_tls_destroy(&g_current_thread_pollset);
-  gpr_tls_destroy(&g_current_thread_worker);
-}
-
-static grpc_error *pollset_worker_kick(grpc_pollset_worker *worker) {
-  gpr_cv_signal(&worker->kick_cv);
-  return GRPC_ERROR_NONE;
-}
-
-/* Return 1 if the pollset has active threads in pollset_work (pollset must
- * be locked) */
-static int pollset_has_workers(grpc_pollset *p) {
-  return p->root_worker.next != &p->root_worker;
-}
-
-static void remove_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->prev->next = worker->next;
-  worker->next->prev = worker->prev;
-}
-
-static grpc_pollset_worker *pop_front_worker(grpc_pollset *p) {
-  if (pollset_has_workers(p)) {
-    grpc_pollset_worker *w = p->root_worker.next;
-    remove_worker(p, w);
-    return w;
-  } else {
-    return NULL;
-  }
-}
-
-static void push_back_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->next = &p->root_worker;
-  worker->prev = worker->next->prev;
-  worker->prev->next = worker->next->prev = worker;
-}
-
-static void push_front_worker(grpc_pollset *p, grpc_pollset_worker *worker) {
-  worker->prev = &p->root_worker;
-  worker->next = worker->prev->next;
-  worker->prev->next = worker->next->prev = worker;
-}
-
-/* p->mu must be held before calling this function */
-static grpc_error *pollset_kick(grpc_pollset *p,
-                                grpc_pollset_worker *specific_worker) {
-  GPR_TIMER_BEGIN("pollset_kick", 0);
-  grpc_error *error = GRPC_ERROR_NONE;
-  const char *err_desc = "Kick Failure";
-  grpc_pollset_worker *worker = specific_worker;
-  if (worker != NULL) {
-    if (worker == GRPC_POLLSET_KICK_BROADCAST) {
-      if (pollset_has_workers(p)) {
-        GPR_TIMER_BEGIN("pollset_kick.broadcast", 0);
-        for (worker = p->root_worker.next; worker != &p->root_worker;
-             worker = worker->next) {
-          if (gpr_tls_get(&g_current_thread_worker) != (intptr_t)worker) {
-            append_error(&error, pollset_worker_kick(worker), err_desc);
-          }
-        }
-        GPR_TIMER_END("pollset_kick.broadcast", 0);
-      } else {
-        p->kicked_without_pollers = true;
-      }
-    } else {
-      GPR_TIMER_MARK("kicked_specifically", 0);
-      if (gpr_tls_get(&g_current_thread_worker) != (intptr_t)worker) {
-        append_error(&error, pollset_worker_kick(worker), err_desc);
-      }
-    }
-  } else if (gpr_tls_get(&g_current_thread_pollset) != (intptr_t)p) {
-    /* Since worker == NULL, it means that we can kick "any" worker on this
-       pollset 'p'. If 'p' happens to be the same pollset this thread is
-       currently polling (i.e in pollset_work() function), then there is no need
-       to kick any other worker since the current thread can just absorb the
-       kick. This is the reason why we enter this case only when
-       g_current_thread_pollset is != p */
-
-    GPR_TIMER_MARK("kick_anonymous", 0);
-    worker = pop_front_worker(p);
-    if (worker != NULL) {
-      GPR_TIMER_MARK("finally_kick", 0);
-      push_back_worker(p, worker);
-      append_error(&error, pollset_worker_kick(worker), err_desc);
-    } else {
-      GPR_TIMER_MARK("kicked_no_pollers", 0);
-      p->kicked_without_pollers = true;
-    }
-  }
-
-  GPR_TIMER_END("pollset_kick", 0);
-  GRPC_LOG_IF_ERROR("pollset_kick", GRPC_ERROR_REF(error));
-  return error;
-}
-
-static void pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
-  gpr_mu_init(&pollset->mu);
-  *mu = &pollset->mu;
-  pollset->eps = NULL;
-
-  pollset->root_worker.next = pollset->root_worker.prev = &pollset->root_worker;
-  pollset->kicked_without_pollers = false;
-
-  pollset->shutting_down = false;
-  pollset->finish_shutdown_called = false;
-  pollset->shutdown_done = NULL;
-}
-
-static void fd_become_readable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
-  grpc_lfev_set_ready(exec_ctx, &fd->read_closure, "read");
-}
-
-static void fd_become_writable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
-  grpc_lfev_set_ready(exec_ctx, &fd->write_closure, "write");
-}
-
-static void pollset_release_epoll_set(grpc_exec_ctx *exec_ctx, grpc_pollset *ps,
-                                      char *reason) {
-  if (ps->eps != NULL) {
-    EPS_UNREF(exec_ctx, ps->eps, reason);
-  }
-  ps->eps = NULL;
-}
-
-static void finish_shutdown_locked(grpc_exec_ctx *exec_ctx,
-                                   grpc_pollset *pollset) {
-  /* The pollset cannot have any workers if we are at this stage */
-  GPR_ASSERT(!pollset_has_workers(pollset));
-
-  pollset->finish_shutdown_called = true;
-
-  /* Release the ref and set pollset->eps to NULL */
-  pollset_release_epoll_set(exec_ctx, pollset, "ps_shutdown");
-  GRPC_CLOSURE_SCHED(exec_ctx, pollset->shutdown_done, GRPC_ERROR_NONE);
-}
-
-/* pollset->mu lock must be held by the caller before calling this */
-static void pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                             grpc_closure *closure) {
-  GPR_TIMER_BEGIN("pollset_shutdown", 0);
-  GPR_ASSERT(!pollset->shutting_down);
-  pollset->shutting_down = true;
-  pollset->shutdown_done = closure;
-  pollset_kick(pollset, GRPC_POLLSET_KICK_BROADCAST);
-
-  /* If the pollset has any workers, we cannot call finish_shutdown_locked()
-     because it would release the underlying epoll set. In such a case, we
-     let the last worker call finish_shutdown_locked() from pollset_work() */
-  if (!pollset_has_workers(pollset)) {
-    GPR_ASSERT(!pollset->finish_shutdown_called);
-    GPR_TIMER_MARK("pollset_shutdown.finish_shutdown_locked", 0);
-    finish_shutdown_locked(exec_ctx, pollset);
-  }
-  GPR_TIMER_END("pollset_shutdown", 0);
-}
-
-/* pollset_shutdown is guaranteed to be called before pollset_destroy. So other
- * than destroying the mutexes, there is nothing special that needs to be done
- * here */
-static void pollset_destroy(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset) {
-  GPR_ASSERT(!pollset_has_workers(pollset));
-  gpr_mu_destroy(&pollset->mu);
-}
-
-/* Blocking call */
-static void acquire_epoll_lease(epoll_set *eps) {
-  if (g_num_threads_per_eps > 1) {
-    gpr_mu_lock(&eps->mu);
-  }
-}
-
-static void release_epoll_lease(epoll_set *eps) {
-  if (g_num_threads_per_eps > 1) {
-    gpr_mu_unlock(&eps->mu);
-  }
-}
-
-#define GRPC_EPOLL_MAX_EVENTS 100
-static void do_epoll_wait(grpc_exec_ctx *exec_ctx, int epoll_fd, epoll_set *eps,
-                          grpc_error **error) {
-  struct epoll_event ep_ev[GRPC_EPOLL_MAX_EVENTS];
-  int ep_rv;
-  char *err_msg;
-  const char *err_desc = "do_epoll_wait";
-
-  int timeout_ms = -1;
-
-  GRPC_SCHEDULING_START_BLOCKING_REGION;
-  acquire_epoll_lease(eps);
-  GRPC_STATS_INC_SYSCALL_POLL(exec_ctx);
-  ep_rv = epoll_wait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, timeout_ms);
-  release_epoll_lease(eps);
-  GRPC_SCHEDULING_END_BLOCKING_REGION;
-
-  if (ep_rv < 0) {
-    gpr_asprintf(&err_msg,
-                 "epoll_wait() epoll fd: %d failed with error: %d (%s)",
-                 epoll_fd, errno, strerror(errno));
-    append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-  }
-
-#ifdef GRPC_TSAN
-  /* See the definition of g_poll_sync for more details */
-  gpr_atm_acq_load(&g_epoll_sync);
-#endif /* defined(GRPC_TSAN) */
-
-  for (int i = 0; i < ep_rv; ++i) {
-    void *data_ptr = ep_ev[i].data.ptr;
-    if (data_ptr == &epoll_set_wakeup_fd) {
-      gpr_atm_rel_store(&eps->is_shutdown, 1);
-      gpr_log(GPR_INFO, "pollset poller: shutdown set");
-    } else {
-      grpc_fd *fd = data_ptr;
-      int cancel = ep_ev[i].events & (EPOLLERR | EPOLLHUP);
-      int read_ev = ep_ev[i].events & (EPOLLIN | EPOLLPRI);
-      int write_ev = ep_ev[i].events & EPOLLOUT;
-      if (read_ev || cancel) {
-        fd_become_readable(exec_ctx, fd);
-      }
-      if (write_ev || cancel) {
-        fd_become_writable(exec_ctx, fd);
-      }
-    }
-  }
-}
-
-static void epoll_set_work(grpc_exec_ctx *exec_ctx, epoll_set *eps,
-                           grpc_error **error) {
-  int epoll_fd = -1;
-  GPR_TIMER_BEGIN("epoll_set_work", 0);
-
-  /* Since epoll_fd is immutable, it is safe to read it without a lock on the
-     epoll set. */
-  epoll_fd = eps->epoll_fd;
-
-  gpr_atm_no_barrier_fetch_add(&eps->poller_count, 1);
-  g_current_thread_epoll_set = eps;
-
-  do_epoll_wait(exec_ctx, epoll_fd, eps, error);
-
-  g_current_thread_epoll_set = NULL;
-  gpr_atm_no_barrier_fetch_add(&eps->poller_count, -1);
-
-  GPR_TIMER_END("epoll_set_work", 0);
-}
-
-/* pollset->mu lock must be held by the caller before calling this.
-   The function pollset_work() may temporarily release the lock (pollset->mu)
-   during the course of its execution but it will always re-acquire the lock and
-   ensure that it is held by the time the function returns */
-static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                                grpc_pollset_worker **worker_hdl,
-                                gpr_timespec now, gpr_timespec deadline) {
-  GPR_TIMER_BEGIN("pollset_work", 0);
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  grpc_pollset_worker worker;
-  pollset_worker_init(&worker);
-
-  if (worker_hdl) *worker_hdl = &worker;
-
-  gpr_tls_set(&g_current_thread_pollset, (intptr_t)pollset);
-  gpr_tls_set(&g_current_thread_worker, (intptr_t)&worker);
-
-  if (pollset->kicked_without_pollers) {
-    /* If the pollset was kicked without pollers, pretend that the current
-       worker got the kick and skip polling. A kick indicates that there is some
-       work that needs attention like an event on the completion queue or an
-       alarm */
-    GPR_TIMER_MARK("pollset_work.kicked_without_pollers", 0);
-    pollset->kicked_without_pollers = 0;
-  } else if (!pollset->shutting_down) {
-    push_front_worker(pollset, &worker);
-
-    gpr_cv_wait(&worker.kick_cv, &pollset->mu,
-                gpr_convert_clock_type(deadline, GPR_CLOCK_REALTIME));
-    /* pollset->mu locked here */
-
-    remove_worker(pollset, &worker);
-  }
-
-  /* If we are the last worker on the pollset (i.e pollset_has_workers() is
-     false at this point) and the pollset is shutting down, we may have to
-     finish the shutdown process by calling finish_shutdown_locked().
-     See pollset_shutdown() for more details.
-
-     Note: Continuing to access pollset here is safe; it is the caller's
-     responsibility to not destroy a pollset when it has outstanding calls to
-     pollset_work() */
-  if (pollset->shutting_down && !pollset_has_workers(pollset) &&
-      !pollset->finish_shutdown_called) {
-    GPR_TIMER_MARK("pollset_work.finish_shutdown_locked", 0);
-    finish_shutdown_locked(exec_ctx, pollset);
-
-    gpr_mu_unlock(&pollset->mu);
-    grpc_exec_ctx_flush(exec_ctx);
-    gpr_mu_lock(&pollset->mu);
-  }
-
-  if (worker_hdl) *worker_hdl = NULL;
-
-  gpr_tls_set(&g_current_thread_pollset, (intptr_t)0);
-  gpr_tls_set(&g_current_thread_worker, (intptr_t)0);
-
-  GPR_TIMER_END("pollset_work", 0);
-
-  GRPC_LOG_IF_ERROR("pollset_work", GRPC_ERROR_REF(error));
-  return error;
-}
-
-static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                           grpc_fd *fd) {
-  /* Nothing to do */
-}
-
-/*******************************************************************************
- * Pollset-set Definitions
- */
-grpc_pollset_set g_dummy_pollset_set;
-static grpc_pollset_set *pollset_set_create(void) {
-  return &g_dummy_pollset_set;
-}
-
-static void pollset_set_destroy(grpc_exec_ctx *exec_ctx,
-                                grpc_pollset_set *pss) {
-  /* Nothing to do */
-}
-
-static void pollset_set_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset_set *pss,
-                               grpc_fd *fd) {
-  /* Nothing to do */
-}
-
-static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx, grpc_pollset_set *pss,
-                               grpc_fd *fd) {
-  /* Nothing to do */
-}
-
-static void pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
-                                    grpc_pollset_set *pss, grpc_pollset *ps) {
-  /* Nothing to do */
-}
-
-static void pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
-                                    grpc_pollset_set *pss, grpc_pollset *ps) {
-  /* Nothing to do */
-}
-
-static void pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
-                                        grpc_pollset_set *bag,
-                                        grpc_pollset_set *item) {
-  /* Nothing to do */
-}
-
-static void pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
-                                        grpc_pollset_set *bag,
-                                        grpc_pollset_set *item) {
-  /* Nothing to do */
-}
-
-/*******************************************************************************
- * Event engine binding
- */
-
-static void shutdown_engine(void) {
-  shutdown_poller_threads();
-  shutdown_epoll_sets();
-  fd_global_shutdown();
-  pollset_global_shutdown();
-  epoll_set_global_shutdown();
-  gpr_log(GPR_INFO, "ev-epoll-threadpool engine shutdown complete");
-}
-
-static const grpc_event_engine_vtable vtable = {
-    .pollset_size = sizeof(grpc_pollset),
-
-    .fd_create = fd_create,
-    .fd_wrapped_fd = fd_wrapped_fd,
-    .fd_orphan = fd_orphan,
-    .fd_shutdown = fd_shutdown,
-    .fd_is_shutdown = fd_is_shutdown,
-    .fd_notify_on_read = fd_notify_on_read,
-    .fd_notify_on_write = fd_notify_on_write,
-    .fd_get_read_notifier_pollset = fd_get_read_notifier_pollset,
-
-    .pollset_init = pollset_init,
-    .pollset_shutdown = pollset_shutdown,
-    .pollset_destroy = pollset_destroy,
-    .pollset_work = pollset_work,
-    .pollset_kick = pollset_kick,
-    .pollset_add_fd = pollset_add_fd,
-
-    .pollset_set_create = pollset_set_create,
-    .pollset_set_destroy = pollset_set_destroy,
-    .pollset_set_add_pollset = pollset_set_add_pollset,
-    .pollset_set_del_pollset = pollset_set_del_pollset,
-    .pollset_set_add_pollset_set = pollset_set_add_pollset_set,
-    .pollset_set_del_pollset_set = pollset_set_del_pollset_set,
-    .pollset_set_add_fd = pollset_set_add_fd,
-    .pollset_set_del_fd = pollset_set_del_fd,
-
-    .shutdown_engine = shutdown_engine,
-};
-
-/*****************************************************************************
- * Dedicated polling threads and pollsets - Definitions
- */
-static void add_fd_to_eps(grpc_fd *fd) {
-  GPR_ASSERT(fd->eps == NULL);
-  GPR_TIMER_BEGIN("add_fd_to_eps", 0);
-
-  grpc_error *error = GRPC_ERROR_NONE;
-  size_t idx = (size_t)gpr_atm_no_barrier_fetch_add(&g_next_eps, 1) % g_num_eps;
-  epoll_set *eps = g_epoll_sets[idx];
-
-  gpr_mu_lock(&fd->mu);
-
-  if (fd->orphaned) {
-    gpr_mu_unlock(&fd->mu);
-    return; /* Early out */
-  }
-
-  epoll_set_add_fd_locked(eps, fd, &error);
-  EPS_ADD_REF(eps, "fd");
-  fd->eps = eps;
-
-  GRPC_POLLING_TRACE("add_fd_to_eps (fd: %d, eps idx = %" PRIdPTR ")", fd->fd,
-                     idx);
-  gpr_mu_unlock(&fd->mu);
-
-  GRPC_LOG_IF_ERROR("add_fd_to_eps", error);
-  GPR_TIMER_END("add_fd_to_eps", 0);
-}
-
-static bool init_epoll_sets() {
-  grpc_error *error = GRPC_ERROR_NONE;
-  bool is_success = true;
-
-  g_epoll_sets = (epoll_set **)malloc(g_num_eps * sizeof(epoll_set *));
-
-  for (size_t i = 0; i < g_num_eps; i++) {
-    g_epoll_sets[i] = epoll_set_create(&error);
-    if (g_epoll_sets[i] == NULL) {
-      gpr_log(GPR_ERROR, "Error in creating a epoll set");
-      g_num_eps = i; /* Helps cleanup */
-      shutdown_epoll_sets();
-      is_success = false;
-      goto done;
-    }
-
-    EPS_ADD_REF(g_epoll_sets[i], "init_epoll_sets");
-  }
-
-  gpr_atm_no_barrier_store(&g_next_eps, 0);
-  gpr_mu *mu;
-  pollset_init(&g_read_notifier, &mu);
-
-done:
-  GRPC_LOG_IF_ERROR("init_epoll_sets", error);
-  return is_success;
-}
-
-static void shutdown_epoll_sets() {
-  if (!g_epoll_sets) {
-    return;
-  }
-
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  for (size_t i = 0; i < g_num_eps; i++) {
-    EPS_UNREF(&exec_ctx, g_epoll_sets[i], "shutdown_epoll_sets");
-  }
-  grpc_exec_ctx_flush(&exec_ctx);
-
-  gpr_free(g_epoll_sets);
-  g_epoll_sets = NULL;
-  pollset_destroy(&exec_ctx, &g_read_notifier);
-  grpc_exec_ctx_finish(&exec_ctx);
-}
-
-static void poller_thread_loop(void *arg) {
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_error *error = GRPC_ERROR_NONE;
-  epoll_set *eps = (epoll_set *)arg;
-
-  while (!gpr_atm_acq_load(&eps->is_shutdown)) {
-    epoll_set_work(&exec_ctx, eps, &error);
-    grpc_exec_ctx_flush(&exec_ctx);
-  }
-
-  grpc_exec_ctx_finish(&exec_ctx);
-  GRPC_LOG_IF_ERROR("poller_thread_loop", error);
-}
-
-/* g_epoll_sets MUST be initialized before calling this */
-static void start_poller_threads() {
-  GPR_ASSERT(g_epoll_sets);
-
-  gpr_log(GPR_INFO, "Starting poller threads");
-
-  size_t num_threads = g_num_eps * g_num_threads_per_eps;
-  g_poller_threads = (gpr_thd_id *)malloc(num_threads * sizeof(gpr_thd_id));
-  gpr_thd_options options = gpr_thd_options_default();
-  gpr_thd_options_set_joinable(&options);
-
-  for (size_t i = 0; i < num_threads; i++) {
-    gpr_thd_new(&g_poller_threads[i], poller_thread_loop,
-                (void *)g_epoll_sets[i % g_num_eps], &options);
-  }
-}
-
-static void shutdown_poller_threads() {
-  GPR_ASSERT(g_poller_threads);
-  GPR_ASSERT(g_epoll_sets);
-  grpc_error *error = GRPC_ERROR_NONE;
-
-  gpr_log(GPR_INFO, "Shutting down pollers");
-
-  epoll_set *eps = NULL;
-  size_t num_threads = g_num_eps * g_num_threads_per_eps;
-  for (size_t i = 0; i < num_threads; i++) {
-    eps = g_epoll_sets[i];
-    epoll_set_add_wakeup_fd_locked(eps, &epoll_set_wakeup_fd, &error);
-  }
-
-  for (size_t i = 0; i < g_num_eps; i++) {
-    gpr_thd_join(g_poller_threads[i]);
-  }
-
-  GRPC_LOG_IF_ERROR("shutdown_poller_threads", error);
-  gpr_free(g_poller_threads);
-  g_poller_threads = NULL;
-}
-
-/****************************************************************************/
-
-/* It is possible that GLIBC has epoll but the underlying kernel doesn't.
- * Create a dummy epoll_fd to make sure epoll support is available */
-static bool is_epoll_available() {
-  int fd = epoll_create1(EPOLL_CLOEXEC);
-  if (fd < 0) {
-    gpr_log(
-        GPR_ERROR,
-        "epoll_create1 failed with error: %d. Not using epoll polling engine",
-        fd);
-    return false;
-  }
-  close(fd);
-  return true;
-}
-
-const grpc_event_engine_vtable *grpc_init_epoll_thread_pool_linux(
-    bool requested_explicitly) {
-  if (!requested_explicitly) return NULL;
-
-  if (!grpc_has_wakeup_fd()) {
-    return NULL;
-  }
-
-  if (!is_epoll_available()) {
-    return NULL;
-  }
-
-  fd_global_init();
-
-  if (!GRPC_LOG_IF_ERROR("pollset_global_init", pollset_global_init())) {
-    return NULL;
-  }
-
-  if (!GRPC_LOG_IF_ERROR("epoll_set_global_init", epoll_set_global_init())) {
-    return NULL;
-  }
-
-  if (!init_epoll_sets()) {
-    return NULL;
-  }
-
-  /* TODO (sreek): Maynot be a good idea to start threads here (especially if
-   * this engine doesn't get picked. Consider introducing an engine_init
-   * function in the vtable */
-  start_poller_threads();
-  return &vtable;
-}
-
-#else /* defined(GRPC_LINUX_EPOLL) */
-#if defined(GRPC_POSIX_SOCKET)
-#include "src/core/lib/iomgr/ev_posix.h"
-/* If GRPC_LINUX_EPOLL is not defined, it means epoll is not available. Return
- * NULL */
-const grpc_event_engine_vtable *grpc_init_epoll_thread_pool_linux(
-    bool requested_explicitly) {
-  return NULL;
-}
-#endif /* defined(GRPC_POSIX_SOCKET) */
-#endif /* !defined(GRPC_LINUX_EPOLL) */
diff --git a/src/core/lib/iomgr/ev_epoll_thread_pool_linux.h b/src/core/lib/iomgr/ev_epoll_thread_pool_linux.h
deleted file mode 100644
index 2ca68cc9d1..0000000000
--- a/src/core/lib/iomgr/ev_epoll_thread_pool_linux.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/*
- *
- * Copyright 2017 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#ifndef GRPC_CORE_LIB_IOMGR_EV_EPOLL_THREAD_POOL_LINUX_H
-#define GRPC_CORE_LIB_IOMGR_EV_EPOLL_THREAD_POOL_LINUX_H
-
-#include "src/core/lib/iomgr/ev_posix.h"
-#include "src/core/lib/iomgr/port.h"
-
-const grpc_event_engine_vtable *grpc_init_epoll_thread_pool_linux(
-    bool requested_explicitly);
-
-#endif /* GRPC_CORE_LIB_IOMGR_EV_EPOLL_THREAD_POOL_LINUX_H */
diff --git a/src/core/lib/iomgr/ev_posix.c b/src/core/lib/iomgr/ev_posix.c
index 424b40e425..bb43061ff5 100644
--- a/src/core/lib/iomgr/ev_posix.c
+++ b/src/core/lib/iomgr/ev_posix.c
@@ -31,8 +31,6 @@
 
 #include "src/core/lib/debug/trace.h"
 #include "src/core/lib/iomgr/ev_epoll1_linux.h"
-#include "src/core/lib/iomgr/ev_epoll_limited_pollers_linux.h"
-#include "src/core/lib/iomgr/ev_epoll_thread_pool_linux.h"
 #include "src/core/lib/iomgr/ev_epollex_linux.h"
 #include "src/core/lib/iomgr/ev_epollsig_linux.h"
 #include "src/core/lib/iomgr/ev_poll_posix.h"
@@ -66,8 +64,6 @@ typedef struct {
 static const event_engine_factory g_factories[] = {
     {"epoll1", grpc_init_epoll1_linux},
     {"epollsig", grpc_init_epollsig_linux},
-    {"epoll-threadpool", grpc_init_epoll_thread_pool_linux},
-    {"epoll-limited", grpc_init_epoll_limited_pollers_linux},
     {"poll", grpc_init_poll_posix},
     {"poll-cv", grpc_init_poll_cv_posix},
     {"epollex", grpc_init_epollex_linux},
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index 1cbf345ab6..a0a1702903 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -85,8 +85,6 @@ CORE_SOURCE_FILES = [
   'src/core/lib/iomgr/endpoint_pair_windows.c',
   'src/core/lib/iomgr/error.c',
   'src/core/lib/iomgr/ev_epoll1_linux.c',
-  'src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c',
-  'src/core/lib/iomgr/ev_epoll_thread_pool_linux.c',
   'src/core/lib/iomgr/ev_epollex_linux.c',
   'src/core/lib/iomgr/ev_epollsig_linux.c',
   'src/core/lib/iomgr/ev_poll_posix.c',