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@ -107,86 +107,116 @@ void grpc_timer_manager_tick() { |
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grpc_exec_ctx_finish(&exec_ctx); |
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} |
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static void timer_thread(void *unused) { |
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// this threads exec_ctx: we try to run things through to completion here
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// since it's easy to spin up new threads
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grpc_exec_ctx exec_ctx = |
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GRPC_EXEC_CTX_INITIALIZER(0, grpc_never_ready_to_finish, NULL); |
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static void run_some_timers(grpc_exec_ctx *exec_ctx) { |
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// if there's something to execute...
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gpr_mu_lock(&g_mu); |
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// remove a waiter from the pool, and start another thread if necessary
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--g_waiter_count; |
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if (g_waiter_count == 0 && g_threaded) { |
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start_timer_thread_and_unlock(); |
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} else { |
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// if there's no thread waiting with a timeout, kick an existing
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// waiter
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// so that the next deadline is not missed
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if (!g_has_timed_waiter) { |
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if (GRPC_TRACER_ON(grpc_timer_check_trace)) { |
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gpr_log(GPR_DEBUG, "kick untimed waiter"); |
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} |
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gpr_cv_signal(&g_cv_wait); |
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} |
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gpr_mu_unlock(&g_mu); |
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} |
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// without our lock, flush the exec_ctx
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grpc_exec_ctx_flush(exec_ctx); |
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gpr_mu_lock(&g_mu); |
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// garbage collect any threads hanging out that are dead
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gc_completed_threads(); |
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// get ready to wait again
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++g_waiter_count; |
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gpr_mu_unlock(&g_mu); |
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} |
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// wait until 'next' (or forever if there is already a timed waiter in the pool)
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// returns true if the thread should continue executing (false if it should
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// shutdown)
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static bool wait_until(gpr_timespec next) { |
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const gpr_timespec inf_future = gpr_inf_future(GPR_CLOCK_MONOTONIC); |
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gpr_mu_lock(&g_mu); |
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// if we're not threaded anymore, leave
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if (!g_threaded) return false; |
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// if there's no timed waiter, we should become one: that waiter waits
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// only until the next timer should expire
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// all other timers wait forever
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uint64_t my_timed_waiter_generation = g_timed_waiter_generation - 1; |
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if (!g_has_timed_waiter && gpr_time_cmp(next, inf_future) != 0) { |
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g_has_timed_waiter = true; |
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// we use a generation counter to track the timed waiter so we can
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// cancel an existing one quickly (and when it actually times out it'll
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// figure stuff out instead of incurring a wakeup)
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my_timed_waiter_generation = ++g_timed_waiter_generation; |
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if (GRPC_TRACER_ON(grpc_timer_check_trace)) { |
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gpr_log(GPR_DEBUG, "sleep for a while"); |
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} |
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} else { |
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next = inf_future; |
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if (GRPC_TRACER_ON(grpc_timer_check_trace)) { |
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gpr_log(GPR_DEBUG, "sleep until kicked"); |
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} |
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} |
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gpr_cv_wait(&g_cv_wait, &g_mu, next); |
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if (GRPC_TRACER_ON(grpc_timer_check_trace)) { |
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gpr_log(GPR_DEBUG, "wait ended: was_timed:%d kicked:%d", |
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my_timed_waiter_generation == g_timed_waiter_generation, g_kicked); |
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} |
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// if this was the timed waiter, then we need to check timers, and flag
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// that there's now no timed waiter... we'll look for a replacement if
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// there's work to do after checking timers (code above)
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if (my_timed_waiter_generation == g_timed_waiter_generation) { |
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g_has_timed_waiter = false; |
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} |
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// if this was a kick from the timer system, consume it (and don't stop
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// this thread yet)
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if (g_kicked) { |
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grpc_timer_consume_kick(); |
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g_kicked = false; |
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} |
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gpr_mu_unlock(&g_mu); |
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return true; |
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} |
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static void timer_main_loop(grpc_exec_ctx *exec_ctx) { |
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const gpr_timespec inf_future = gpr_inf_future(GPR_CLOCK_MONOTONIC); |
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for (;;) { |
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gpr_timespec next = inf_future; |
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gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC); |
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// check timer state, updates next to the next time to run a check
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if (grpc_timer_check(&exec_ctx, now, &next)) { |
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// if there's something to execute...
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gpr_mu_lock(&g_mu); |
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// remove a waiter from the pool, and start another thread if necessary
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--g_waiter_count; |
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if (g_waiter_count == 0 && g_threaded) { |
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start_timer_thread_and_unlock(); |
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} else { |
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// if there's no thread waiting with a timeout, kick an existing waiter
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// so that the next deadline is not missed
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if (!g_has_timed_waiter) { |
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if (GRPC_TRACER_ON(grpc_timer_check_trace)) { |
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gpr_log(GPR_DEBUG, "kick untimed waiter"); |
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} |
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gpr_cv_signal(&g_cv_wait); |
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} |
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gpr_mu_unlock(&g_mu); |
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} |
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// without our lock, flush the exec_ctx
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grpc_exec_ctx_flush(&exec_ctx); |
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gpr_mu_lock(&g_mu); |
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// garbage collect any threads hanging out that are dead
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gc_completed_threads(); |
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// get ready to wait again
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++g_waiter_count; |
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gpr_mu_unlock(&g_mu); |
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} else { |
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gpr_mu_lock(&g_mu); |
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// if we're not threaded anymore, leave
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if (!g_threaded) break; |
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// if there's no timed waiter, we should become one: that waiter waits
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// only until the next timer should expire
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// all other timers wait forever
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uint64_t my_timed_waiter_generation = g_timed_waiter_generation - 1; |
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if (!g_has_timed_waiter) { |
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g_has_timed_waiter = true; |
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// we use a generation counter to track the timed waiter so we can
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// cancel an existing one quickly (and when it actually times out it'll
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// figure stuff out instead of incurring a wakeup)
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my_timed_waiter_generation = ++g_timed_waiter_generation; |
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if (GRPC_TRACER_ON(grpc_timer_check_trace)) { |
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gpr_log(GPR_DEBUG, "sleep for a while"); |
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} |
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} else { |
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switch (grpc_timer_check(exec_ctx, now, &next)) { |
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case GRPC_TIMERS_FIRED: |
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run_some_timers(exec_ctx); |
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break; |
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case GRPC_TIMERS_NOT_CHECKED: |
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/* This case only happens under contention, meaning more than one timer
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manager thread checked timers concurrently. |
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If that happens, we're guaranteed that some other thread has just |
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checked timers, and this will avalanche into some other thread seeing |
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empty timers and doing a timed sleep. |
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Consequently, we can just sleep forever here and be happy at some |
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saved wakeup cycles. */ |
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next = inf_future; |
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if (GRPC_TRACER_ON(grpc_timer_check_trace)) { |
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gpr_log(GPR_DEBUG, "sleep until kicked"); |
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/* fall through */ |
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case GRPC_TIMERS_CHECKED_AND_EMPTY: |
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if (!wait_until(next)) { |
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return; |
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} |
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} |
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gpr_cv_wait(&g_cv_wait, &g_mu, next); |
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if (GRPC_TRACER_ON(grpc_timer_check_trace)) { |
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gpr_log(GPR_DEBUG, "wait ended: was_timed:%d kicked:%d", |
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my_timed_waiter_generation == g_timed_waiter_generation, |
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g_kicked); |
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} |
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// if this was the timed waiter, then we need to check timers, and flag
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// that there's now no timed waiter... we'll look for a replacement if
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// there's work to do after checking timers (code above)
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if (my_timed_waiter_generation == g_timed_waiter_generation) { |
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g_has_timed_waiter = false; |
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} |
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// if this was a kick from the timer system, consume it (and don't stop
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// this thread yet)
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if (g_kicked) { |
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grpc_timer_consume_kick(); |
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g_kicked = false; |
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} |
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gpr_mu_unlock(&g_mu); |
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break; |
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} |
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} |
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} |
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static void timer_thread_cleanup(void) { |
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gpr_mu_lock(&g_mu); |
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// terminate the thread: drop the waiter count, thread count, and let whomever
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// stopped the threading stuff know that we're done
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--g_waiter_count; |
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@ -199,12 +229,21 @@ static void timer_thread(void *unused) { |
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ct->next = g_completed_threads; |
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g_completed_threads = ct; |
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gpr_mu_unlock(&g_mu); |
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grpc_exec_ctx_finish(&exec_ctx); |
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if (GRPC_TRACER_ON(grpc_timer_check_trace)) { |
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gpr_log(GPR_DEBUG, "End timer thread"); |
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} |
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} |
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static void timer_thread(void *unused) { |
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// this threads exec_ctx: we try to run things through to completion here
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// since it's easy to spin up new threads
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grpc_exec_ctx exec_ctx = |
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GRPC_EXEC_CTX_INITIALIZER(0, grpc_never_ready_to_finish, NULL); |
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timer_main_loop(&exec_ctx); |
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grpc_exec_ctx_finish(&exec_ctx); |
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timer_thread_cleanup(); |
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} |
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static void start_threads(void) { |
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gpr_mu_lock(&g_mu); |
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if (!g_threaded) { |
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Craig Tiller
8 years ago