diff options
Diffstat (limited to 'src/core/lib/iomgr/ev_epollsig_linux.cc')
-rw-r--r-- | src/core/lib/iomgr/ev_epollsig_linux.cc | 1769 |
1 files changed, 1769 insertions, 0 deletions
diff --git a/src/core/lib/iomgr/ev_epollsig_linux.cc b/src/core/lib/iomgr/ev_epollsig_linux.cc new file mode 100644 index 0000000000..c8e07c6e18 --- /dev/null +++ b/src/core/lib/iomgr/ev_epollsig_linux.cc @@ -0,0 +1,1769 @@ +/* + * + * Copyright 2016 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_epollsig_linux.h" + +#include <assert.h> +#include <errno.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/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" + +#define GRPC_POLLSET_KICK_BROADCAST ((grpc_pollset_worker *)1) + +#define GRPC_POLLING_TRACE(...) \ + if (GRPC_TRACER_ON(grpc_polling_trace)) { \ + gpr_log(GPR_INFO, __VA_ARGS__); \ + } + +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 */ +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; + +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 + +/* 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 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 + */ +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; +}; + +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 */ + } + } +} + +/* 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 = + (grpc_fd **)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 = (polling_island *)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); + + 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_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 = (grpc_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); + 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"); + } + if (error != GRPC_ERROR_NONE) { + const char *msg = grpc_error_string(error); + gpr_log(GPR_DEBUG, "fd_orphan: %s", msg); + } + 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 void sig_handler(int sig_num) { +#ifdef GRPC_EPOLL_DEBUG + gpr_log(GPR_INFO, "Received signal %d", sig_num); +#endif +} + +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 *pollset_worker_kick(grpc_pollset_worker *worker) { + grpc_error *err = GRPC_ERROR_NONE; + + /* Kick the worker only if it was not already kicked */ + if (gpr_atm_no_barrier_cas(&worker->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; +} + +/* 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_exec_ctx *exec_ctx, grpc_pollset *p, + grpc_pollset_worker *specific_worker) { + GPR_TIMER_BEGIN("pollset_kick", 0); + grpc_error *error = GRPC_ERROR_NONE; + GRPC_STATS_INC_POLLSET_KICK(exec_ctx); + 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 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, + const 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(exec_ctx, 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); +} + +#define GRPC_EPOLL_MAX_EVENTS 100 +/* 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, int timeout_ms, + sigset_t *sig_mask, grpc_error **error) { + struct epoll_event ep_ev[GRPC_EPOLL_MAX_EVENTS]; + int epoll_fd = -1; + int ep_rv; + polling_island *pi = NULL; + char *err_msg; + const char *err_desc = "pollset_work_and_unlock"; + 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, we can read it without obtaining the polling + island lock. There is however a possibility that the polling island (from + which we got the epoll_fd) got merged with another island while we are + in this function. This is still okay because in such a case, we will wakeup + right-away from epoll_wait() and pick up the latest polling_island the next + this function (i.e 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. We 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); + + gpr_atm_no_barrier_fetch_add(&pi->poller_count, 1); + g_current_thread_polling_island = pi; + + 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; + 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 = (grpc_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); + } + } + } + + g_current_thread_polling_island = NULL; + gpr_atm_no_barrier_fetch_add(&pi->poller_count, -1); + + 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; + int timeout_ms = poll_deadline_to_millis_timeout(deadline, now); + + sigset_t new_mask; + + grpc_pollset_worker worker; + worker.next = worker.prev = NULL; + worker.pt_id = pthread_self(); + gpr_atm_no_barrier_store(&worker.is_kicked, (gpr_atm)0); + + 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(&new_mask); + sigaddset(&new_mask, grpc_wakeup_signal); + pthread_sigmask(SIG_BLOCK, &new_mask, &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, timeout_ms, + &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 = (grpc_pollset_set *)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 */ +} + +/* Test helper functions + * */ +void *grpc_fd_get_polling_island(grpc_fd *fd) { + polling_island *pi; + + gpr_mu_lock(&fd->po.mu); + pi = fd->po.pi; + gpr_mu_unlock(&fd->po.mu); + + return pi; +} + +void *grpc_pollset_get_polling_island(grpc_pollset *ps) { + polling_island *pi; + + gpr_mu_lock(&ps->po.mu); + pi = ps->po.pi; + gpr_mu_unlock(&ps->po.mu); + + return pi; +} + +bool grpc_are_polling_islands_equal(void *p, void *q) { + polling_island *p1 = (polling_island *)p; + polling_island *p2 = (polling_island *)q; + + /* Note: polling_island_lock_pair() may change p1 and p2 to point to the + latest polling islands in their respective linked lists */ + polling_island_lock_pair(&p1, &p2); + polling_island_unlock_pair(p1, p2); + + return p1 == p2; +} + +/******************************************************************************* + * 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 = { + sizeof(grpc_pollset), + + fd_create, + fd_wrapped_fd, + fd_orphan, + fd_shutdown, + fd_notify_on_read, + fd_notify_on_write, + fd_is_shutdown, + fd_get_read_notifier_pollset, + + pollset_init, + pollset_shutdown, + pollset_destroy, + pollset_work, + pollset_kick, + pollset_add_fd, + + pollset_set_create, + pollset_set_destroy, + pollset_set_add_pollset, + pollset_set_del_pollset, + pollset_set_add_pollset_set, + pollset_set_del_pollset_set, + pollset_set_add_fd, + pollset_set_del_fd, + + 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; +} + +const grpc_event_engine_vtable *grpc_init_epollsig_linux( + bool explicit_request) { + /* 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) { + if (explicit_request) { + grpc_use_signal(SIGRTMIN + 6); + } else { + return NULL; + } + } + + 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_epollsig_linux.h" +/* If GRPC_LINUX_EPOLL is not defined, it means epoll is not available. Return + * NULL */ +const grpc_event_engine_vtable *grpc_init_epollsig_linux( + bool explicit_request) { + return NULL; +} +#endif /* defined(GRPC_POSIX_SOCKET) */ + +void grpc_use_signal(int signum) {} +#endif /* !defined(GRPC_LINUX_EPOLL) */ |