diff options
Diffstat (limited to 'src/core/lib/iomgr/ev_epoll_thread_pool_linux.c')
| -rw-r--r-- | src/core/lib/iomgr/ev_epoll_thread_pool_linux.c | 1182 |
1 files changed, 1182 insertions, 0 deletions
diff --git a/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c b/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c new file mode 100644 index 0000000000..49be72c03e --- /dev/null +++ b/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c @@ -0,0 +1,1182 @@ +/* + * + * 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/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, + const char *reason) { + bool is_fd_closed = false; + 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 { + 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); +} + +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); +} + +/******************************************************************************* + * 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); +} + +static void fd_become_writable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) { + grpc_lfev_set_ready(exec_ctx, &fd->write_closure); +} + +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); + 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) */ |