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/*
*
* Copyright 2015, 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/executor.h"
#include <string.h>
#include <grpc/support/alloc.h>
#include <grpc/support/cpu.h>
#include <grpc/support/log.h>
#include <grpc/support/sync.h>
#include <grpc/support/thd.h>
#include <grpc/support/tls.h>
#include <grpc/support/useful.h>
#include "src/core/lib/iomgr/exec_ctx.h"
#include "src/core/lib/support/spinlock.h"
#define MAX_DEPTH 2
typedef struct {
gpr_mu mu;
gpr_cv cv;
grpc_closure_list elems;
size_t depth;
bool shutdown;
gpr_thd_id id;
} thread_state;
static thread_state *g_thread_state;
static size_t g_max_threads;
static gpr_atm g_cur_threads;
static gpr_spinlock g_adding_thread_lock = GPR_SPINLOCK_STATIC_INITIALIZER;
GPR_TLS_DECL(g_this_thread_state);
static void executor_thread(void *arg);
static size_t run_closures(grpc_exec_ctx *exec_ctx, grpc_closure_list list) {
size_t n = 0;
grpc_closure *c = list.head;
while (c != NULL) {
grpc_closure *next = c->next_data.next;
grpc_error *error = c->error_data.error;
#ifndef NDEBUG
c->scheduled = false;
#endif
c->cb(exec_ctx, c->cb_arg, error);
GRPC_ERROR_UNREF(error);
c = next;
}
return n;
}
bool grpc_executor_is_threaded() {
return gpr_atm_no_barrier_load(&g_cur_threads) > 0;
}
void grpc_executor_set_threading(grpc_exec_ctx *exec_ctx, bool threading) {
gpr_atm cur_threads = gpr_atm_no_barrier_load(&g_cur_threads);
if (threading) {
if (cur_threads > 0) return;
g_max_threads = GPR_MAX(1, 2 * gpr_cpu_num_cores());
gpr_atm_no_barrier_store(&g_cur_threads, 1);
gpr_tls_init(&g_this_thread_state);
g_thread_state = gpr_zalloc(sizeof(thread_state) * g_max_threads);
for (size_t i = 0; i < g_max_threads; i++) {
gpr_mu_init(&g_thread_state[i].mu);
gpr_cv_init(&g_thread_state[i].cv);
g_thread_state[i].elems = (grpc_closure_list)GRPC_CLOSURE_LIST_INIT;
}
gpr_thd_options opt = gpr_thd_options_default();
gpr_thd_options_set_joinable(&opt);
gpr_thd_new(&g_thread_state[0].id, executor_thread, &g_thread_state[0],
&opt);
} else {
if (cur_threads == 0) return;
for (size_t i = 0; i < g_max_threads; i++) {
gpr_mu_lock(&g_thread_state[i].mu);
g_thread_state[i].shutdown = true;
gpr_cv_signal(&g_thread_state[i].cv);
gpr_mu_unlock(&g_thread_state[i].mu);
}
/* ensure no thread is adding a new thread... once this is past, then
no thread will try to add a new one either (since shutdown is true) */
gpr_spinlock_lock(&g_adding_thread_lock);
gpr_spinlock_unlock(&g_adding_thread_lock);
for (gpr_atm i = 0; i < g_cur_threads; i++) {
gpr_thd_join(g_thread_state[i].id);
}
gpr_atm_no_barrier_store(&g_cur_threads, 0);
for (size_t i = 0; i < g_max_threads; i++) {
gpr_mu_destroy(&g_thread_state[i].mu);
gpr_cv_destroy(&g_thread_state[i].cv);
run_closures(exec_ctx, g_thread_state[i].elems);
}
gpr_free(g_thread_state);
gpr_tls_destroy(&g_this_thread_state);
}
}
void grpc_executor_init(grpc_exec_ctx *exec_ctx) {
gpr_atm_no_barrier_store(&g_cur_threads, 0);
grpc_executor_set_threading(exec_ctx, true);
}
void grpc_executor_shutdown(grpc_exec_ctx *exec_ctx) {
grpc_executor_set_threading(exec_ctx, false);
}
static void executor_thread(void *arg) {
thread_state *ts = arg;
gpr_tls_set(&g_this_thread_state, (intptr_t)ts);
grpc_exec_ctx exec_ctx =
GRPC_EXEC_CTX_INITIALIZER(0, grpc_never_ready_to_finish, NULL);
size_t subtract_depth = 0;
for (;;) {
gpr_mu_lock(&ts->mu);
ts->depth -= subtract_depth;
while (grpc_closure_list_empty(ts->elems) && !ts->shutdown) {
gpr_cv_wait(&ts->cv, &ts->mu, gpr_inf_future(GPR_CLOCK_REALTIME));
}
if (ts->shutdown) {
gpr_mu_unlock(&ts->mu);
break;
}
grpc_closure_list exec = ts->elems;
ts->elems = (grpc_closure_list)GRPC_CLOSURE_LIST_INIT;
gpr_mu_unlock(&ts->mu);
subtract_depth = run_closures(&exec_ctx, exec);
grpc_exec_ctx_flush(&exec_ctx);
}
grpc_exec_ctx_finish(&exec_ctx);
}
static void executor_push(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
grpc_error *error) {
size_t cur_thread_count = (size_t)gpr_atm_no_barrier_load(&g_cur_threads);
if (cur_thread_count == 0) {
grpc_closure_list_append(&exec_ctx->closure_list, closure, error);
return;
}
thread_state *ts = (thread_state *)gpr_tls_get(&g_this_thread_state);
if (ts == NULL) {
ts = &g_thread_state[GPR_HASH_POINTER(exec_ctx, cur_thread_count)];
}
gpr_mu_lock(&ts->mu);
if (grpc_closure_list_empty(ts->elems)) {
gpr_cv_signal(&ts->cv);
}
grpc_closure_list_append(&ts->elems, closure, error);
ts->depth++;
bool try_new_thread = ts->depth > MAX_DEPTH &&
cur_thread_count < g_max_threads && !ts->shutdown;
if (try_new_thread && gpr_spinlock_trylock(&g_adding_thread_lock)) {
gpr_mu_unlock(&ts->mu);
cur_thread_count = (size_t)gpr_atm_no_barrier_load(&g_cur_threads);
if (cur_thread_count < g_max_threads) {
gpr_atm_no_barrier_store(&g_cur_threads, cur_thread_count + 1);
gpr_thd_options opt = gpr_thd_options_default();
gpr_thd_options_set_joinable(&opt);
gpr_thd_new(&g_thread_state[cur_thread_count].id, executor_thread,
&g_thread_state[cur_thread_count], &opt);
}
gpr_spinlock_unlock(&g_adding_thread_lock);
} else {
gpr_mu_unlock(&ts->mu);
}
}
static const grpc_closure_scheduler_vtable executor_vtable = {
executor_push, executor_push, "executor"};
static grpc_closure_scheduler executor_scheduler = {&executor_vtable};
grpc_closure_scheduler *grpc_executor_scheduler = &executor_scheduler;
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