diff options
Diffstat (limited to 'src/core/lib/iomgr/timer_manager.c')
-rw-r--r-- | src/core/lib/iomgr/timer_manager.c | 225 |
1 files changed, 128 insertions, 97 deletions
diff --git a/src/core/lib/iomgr/timer_manager.c b/src/core/lib/iomgr/timer_manager.c index fd9a7a2f04..3154ddd7f5 100644 --- a/src/core/lib/iomgr/timer_manager.c +++ b/src/core/lib/iomgr/timer_manager.c @@ -1,33 +1,18 @@ /* * - * Copyright 2017, Google Inc. - * All rights reserved. + * Copyright 2017 gRPC authors. * - * Redistribution and use in source and binary forms, with or without - * modification, are permitted provided that the following conditions are - * met: + * 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 * - * * 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. + * http://www.apache.org/licenses/LICENSE-2.0 * - * 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. + * 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. * */ @@ -68,7 +53,7 @@ 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 timer_thread(void *completed_thread_ptr); static void gc_completed_threads(void) { if (g_completed_threads != NULL) { @@ -107,86 +92,124 @@ void grpc_timer_manager_tick() { grpc_exec_ctx_finish(&exec_ctx); } -static void timer_thread(void *completed_thread_ptr) { - // 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); +static void run_some_timers(grpc_exec_ctx *exec_ctx) { + // 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; + if (g_waiter_count == 0 && 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) { + if (GRPC_TRACER_ON(grpc_timer_check_trace)) { + 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); +} + +// wait until 'next' (or forever if there is already a timed waiter in the pool) +// returns true if the thread should continue executing (false if it should +// shutdown) +static bool wait_until(gpr_timespec next) { + const gpr_timespec inf_future = gpr_inf_future(GPR_CLOCK_MONOTONIC); + gpr_mu_lock(&g_mu); + // if we're not threaded anymore, leave + if (!g_threaded) { + gpr_mu_unlock(&g_mu); + return false; + } + // 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 && gpr_time_cmp(next, inf_future) != 0) { + 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; + if (GRPC_TRACER_ON(grpc_timer_check_trace)) { + gpr_timespec wait_time = gpr_time_sub(next, gpr_now(GPR_CLOCK_MONOTONIC)); + gpr_log(GPR_DEBUG, "sleep for a %" PRId64 ".%09d seconds", + wait_time.tv_sec, wait_time.tv_nsec); + } + } else { + next = inf_future; + if (GRPC_TRACER_ON(grpc_timer_check_trace)) { + gpr_log(GPR_DEBUG, "sleep until kicked"); + } + } + gpr_cv_wait(&g_cv_wait, &g_mu, next); + if (GRPC_TRACER_ON(grpc_timer_check_trace)) { + 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); + return true; +} + +static void timer_main_loop(grpc_exec_ctx *exec_ctx) { 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; - if (g_waiter_count == 0 && 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) { - if (GRPC_TRACER_ON(grpc_timer_check_trace)) { - 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; + switch (grpc_timer_check(exec_ctx, now, &next)) { + case GRPC_TIMERS_FIRED: + run_some_timers(exec_ctx); + break; + case GRPC_TIMERS_NOT_CHECKED: + /* This case only happens under contention, meaning more than one timer + manager thread checked timers concurrently. + + If that happens, we're guaranteed that some other thread has just + checked timers, and this will avalanche into some other thread seeing + empty timers and doing a timed sleep. + + Consequently, we can just sleep forever here and be happy at some + saved wakeup cycles. */ if (GRPC_TRACER_ON(grpc_timer_check_trace)) { - gpr_log(GPR_DEBUG, "sleep for a while"); + gpr_log(GPR_DEBUG, "timers not checked: expect another thread to"); } - } else { next = inf_future; - if (GRPC_TRACER_ON(grpc_timer_check_trace)) { - gpr_log(GPR_DEBUG, "sleep until kicked"); + /* fall through */ + case GRPC_TIMERS_CHECKED_AND_EMPTY: + if (!wait_until(next)) { + return; } - } - gpr_cv_wait(&g_cv_wait, &g_mu, next); - if (GRPC_TRACER_ON(grpc_timer_check_trace)) { - 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); + break; } } +} + +static void timer_thread_cleanup(completed_thread *ct) { + gpr_mu_lock(&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; @@ -194,16 +217,24 @@ static void timer_thread(void *completed_thread_ptr) { if (0 == g_thread_count) { gpr_cv_signal(&g_cv_shutdown); } - completed_thread *ct = completed_thread_ptr; ct->next = g_completed_threads; g_completed_threads = ct; gpr_mu_unlock(&g_mu); - grpc_exec_ctx_finish(&exec_ctx); if (GRPC_TRACER_ON(grpc_timer_check_trace)) { gpr_log(GPR_DEBUG, "End timer thread"); } } +static void timer_thread(void *completed_thread_ptr) { + // 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); + timer_main_loop(&exec_ctx); + grpc_exec_ctx_finish(&exec_ctx); + timer_thread_cleanup(completed_thread_ptr); +} + static void start_threads(void) { gpr_mu_lock(&g_mu); if (!g_threaded) { |