| /* |
| * |
| * Copyright 2017, Google Inc. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following disclaimer |
| * in the documentation and/or other materials provided with the |
| * distribution. |
| * * Neither the name of Google Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| */ |
| |
| #include "src/core/lib/iomgr/timer_manager.h" |
| |
| #include <grpc/support/alloc.h> |
| #include <grpc/support/log.h> |
| #include <grpc/support/thd.h> |
| |
| #include "src/core/lib/iomgr/timer.h" |
| |
| typedef struct completed_thread { |
| gpr_thd_id t; |
| struct completed_thread *next; |
| } completed_thread; |
| |
| // global mutex |
| static gpr_mu g_mu; |
| // are we multi-threaded |
| static bool g_threaded; |
| // cv to wait until a thread is needed |
| static gpr_cv g_cv_wait; |
| // cv for notification when threading ends |
| static gpr_cv g_cv_shutdown; |
| // number of threads in the system |
| static int g_thread_count; |
| // number of threads sitting around waiting |
| static int g_waiter_count; |
| // linked list of threads that have completed (and need joining) |
| static completed_thread *g_completed_threads; |
| // was the manager kicked by the timer system |
| static bool g_kicked; |
| // is there a thread waiting until the next timer should fire? |
| static bool g_has_timed_waiter; |
| // generation counter to track which thread is waiting for the next timer |
| static uint64_t g_timed_waiter_generation; |
| |
| static void timer_thread(void *unused); |
| |
| static void gc_completed_threads(void) { |
| if (g_completed_threads != NULL) { |
| completed_thread *to_gc = g_completed_threads; |
| g_completed_threads = NULL; |
| gpr_mu_unlock(&g_mu); |
| while (to_gc != NULL) { |
| gpr_thd_join(to_gc->t); |
| completed_thread *next = to_gc->next; |
| gpr_free(to_gc); |
| to_gc = next; |
| } |
| gpr_mu_lock(&g_mu); |
| } |
| } |
| |
| static void start_timer_thread_and_unlock(void) { |
| ++g_waiter_count; |
| ++g_thread_count; |
| gpr_mu_unlock(&g_mu); |
| gpr_log(GPR_DEBUG, "Spawn timer thread"); |
| gpr_thd_id thd; |
| gpr_thd_options opt = gpr_thd_options_default(); |
| gpr_thd_options_set_joinable(&opt); |
| gpr_thd_new(&thd, timer_thread, NULL, &opt); |
| } |
| |
| void grpc_timer_manager_tick() { |
| grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT; |
| gpr_timespec next = gpr_inf_future(GPR_CLOCK_MONOTONIC); |
| gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC); |
| grpc_timer_check(&exec_ctx, now, &next); |
| grpc_exec_ctx_finish(&exec_ctx); |
| } |
| |
| static void timer_thread(void *unused) { |
| // this threads exec_ctx: we try to run things through to completion here |
| // since it's easy to spin up new threads |
| grpc_exec_ctx exec_ctx = |
| GRPC_EXEC_CTX_INITIALIZER(0, grpc_never_ready_to_finish, NULL); |
| const gpr_timespec inf_future = gpr_inf_future(GPR_CLOCK_MONOTONIC); |
| for (;;) { |
| gpr_timespec next = inf_future; |
| gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC); |
| // check timer state, updates next to the next time to run a check |
| if (grpc_timer_check(&exec_ctx, now, &next)) { |
| // if there's something to execute... |
| gpr_mu_lock(&g_mu); |
| // remove a waiter from the pool, and start another thread if necessary |
| --g_waiter_count; |
| bool start_thread = g_waiter_count == 0; |
| if (start_thread && g_threaded) { |
| start_timer_thread_and_unlock(); |
| } else { |
| // if there's no thread waiting with a timeout, kick an existing waiter |
| // so that the next deadline is not missed |
| if (!g_has_timed_waiter) { |
| gpr_log(GPR_DEBUG, "kick untimed waiter"); |
| gpr_cv_signal(&g_cv_wait); |
| } |
| gpr_mu_unlock(&g_mu); |
| } |
| // without our lock, flush the exec_ctx |
| grpc_exec_ctx_flush(&exec_ctx); |
| gpr_mu_lock(&g_mu); |
| // garbage collect any threads hanging out that are dead |
| gc_completed_threads(); |
| // get ready to wait again |
| ++g_waiter_count; |
| gpr_mu_unlock(&g_mu); |
| } else { |
| gpr_mu_lock(&g_mu); |
| // if we're not threaded anymore, leave |
| if (!g_threaded) break; |
| // if there's no timed waiter, we should become one: that waiter waits |
| // only until the next timer should expire |
| // all other timers wait forever |
| uint64_t my_timed_waiter_generation = g_timed_waiter_generation - 1; |
| if (!g_has_timed_waiter) { |
| g_has_timed_waiter = true; |
| // we use a generation counter to track the timed waiter so we can |
| // cancel an existing one quickly (and when it actually times out it'll |
| // figure stuff out instead of incurring a wakeup) |
| my_timed_waiter_generation = ++g_timed_waiter_generation; |
| gpr_log(GPR_DEBUG, "sleep for a while"); |
| } else { |
| next = inf_future; |
| gpr_log(GPR_DEBUG, "sleep until kicked"); |
| } |
| gpr_cv_wait(&g_cv_wait, &g_mu, next); |
| gpr_log(GPR_DEBUG, "wait ended: was_timed:%d kicked:%d", |
| my_timed_waiter_generation == g_timed_waiter_generation, |
| g_kicked); |
| // if this was the timed waiter, then we need to check timers, and flag |
| // that there's now no timed waiter... we'll look for a replacement if |
| // there's work to do after checking timers (code above) |
| if (my_timed_waiter_generation == g_timed_waiter_generation) { |
| g_has_timed_waiter = false; |
| } |
| // if this was a kick from the timer system, consume it (and don't stop |
| // this thread yet) |
| if (g_kicked) { |
| grpc_timer_consume_kick(); |
| g_kicked = false; |
| } |
| } |
| gpr_mu_unlock(&g_mu); |
| } |
| // terminate the thread: drop the waiter count, thread count, and let whomever |
| // stopped the threading stuff know that we're done |
| --g_waiter_count; |
| --g_thread_count; |
| if (0 == g_thread_count) { |
| gpr_cv_signal(&g_cv_shutdown); |
| } |
| completed_thread *ct = gpr_malloc(sizeof(*ct)); |
| ct->t = gpr_thd_currentid(); |
| ct->next = g_completed_threads; |
| g_completed_threads = ct; |
| gpr_mu_unlock(&g_mu); |
| grpc_exec_ctx_finish(&exec_ctx); |
| gpr_log(GPR_DEBUG, "End timer thread"); |
| } |
| |
| static void start_threads(void) { |
| gpr_mu_lock(&g_mu); |
| if (!g_threaded) { |
| g_threaded = true; |
| start_timer_thread_and_unlock(); |
| } else { |
| g_threaded = false; |
| gpr_mu_unlock(&g_mu); |
| } |
| } |
| |
| void grpc_timer_manager_init(void) { |
| gpr_mu_init(&g_mu); |
| gpr_cv_init(&g_cv_wait); |
| gpr_cv_init(&g_cv_shutdown); |
| g_threaded = false; |
| g_thread_count = 0; |
| g_waiter_count = 0; |
| g_completed_threads = NULL; |
| |
| start_threads(); |
| } |
| |
| static void stop_threads(void) { |
| gpr_mu_lock(&g_mu); |
| if (g_threaded) { |
| g_threaded = false; |
| gpr_cv_broadcast(&g_cv_wait); |
| while (g_thread_count > 0) { |
| gpr_cv_wait(&g_cv_shutdown, &g_mu, gpr_inf_future(GPR_CLOCK_REALTIME)); |
| gc_completed_threads(); |
| } |
| } |
| gpr_mu_unlock(&g_mu); |
| } |
| |
| void grpc_timer_manager_shutdown(void) { |
| stop_threads(); |
| |
| gpr_mu_destroy(&g_mu); |
| gpr_cv_destroy(&g_cv_wait); |
| gpr_cv_destroy(&g_cv_shutdown); |
| } |
| |
| void grpc_timer_manager_set_threading(bool threaded) { |
| if (threaded) { |
| start_threads(); |
| } else { |
| stop_threads(); |
| } |
| } |
| |
| void grpc_kick_poller(void) { |
| gpr_mu_lock(&g_mu); |
| g_kicked = true; |
| g_has_timed_waiter = false; |
| ++g_timed_waiter_generation; |
| gpr_cv_signal(&g_cv_wait); |
| gpr_mu_unlock(&g_mu); |
| } |