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Add pthread thread-local storage support for ScopedYieldPolicy

Browse source 
Emscripten does not support C++11 thread_local but does support
the pthread TLS API.

Bug: None
Change-Id: Ia21895148d1df7652579d086d9e1c0c53d7a85f4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/145441
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28621}
This commit is contained in:
Steve Anton 2019-07-19 07:03:03 -07:00 committed by Commit Bot
parent 836ab13f1c
commit fefa77c426
2 changed files with 57 additions and 5 deletions
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2
rtc_base/synchronization/BUILD.gn
View file

@ -56,6 +56,8 @@ rtc_source_set("yield_policy") {
"yield_policy.h",
]
deps = [
"..:checks",
"//third_party/abseil-cpp/absl/base:config",
"//third_party/abseil-cpp/absl/base:core_headers",
]
}

60
rtc_base/synchronization/yield_policy.cc
View file

@ -10,23 +10,73 @@
#include "rtc_base/synchronization/yield_policy.h"
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "rtc_base/checks.h"
#if !defined(ABSL_HAVE_THREAD_LOCAL) && defined(WEBRTC_POSIX)
#include <pthread.h>
#endif
namespace rtc {
namespace {
#if defined(ABSL_HAVE_THREAD_LOCAL)
ABSL_CONST_INIT thread_local YieldInterface* current_yield_policy = nullptr;
YieldInterface* GetCurrentYieldPolicy() {
return current_yield_policy;
}
void SetCurrentYieldPolicy(YieldInterface* ptr) {
current_yield_policy = ptr;
}
#elif defined(WEBRTC_POSIX)
// Emscripten does not support the C++11 thread_local keyword but does support
// the pthread thread-local storage API.
// https://github.com/emscripten-core/emscripten/issues/3502
ABSL_CONST_INIT pthread_key_t g_current_yield_policy_tls = 0;
void InitializeTls() {
RTC_CHECK_EQ(pthread_key_create(&g_current_yield_policy_tls, nullptr), 0);
}
pthread_key_t GetCurrentYieldPolicyTls() {
static pthread_once_t init_once = PTHREAD_ONCE_INIT;
RTC_CHECK_EQ(pthread_once(&init_once, &InitializeTls), 0);
return g_current_yield_policy_tls;
}
YieldInterface* GetCurrentYieldPolicy() {
return static_cast<YieldInterface*>(
pthread_getspecific(GetCurrentYieldPolicyTls()));
}
void SetCurrentYieldPolicy(YieldInterface* ptr) {
pthread_setspecific(GetCurrentYieldPolicyTls(), ptr);
}
#else
#error Unsupported platform
#endif
} // namespace
ScopedYieldPolicy::ScopedYieldPolicy(YieldInterface* policy)
: previous_(current_yield_policy) {
current_yield_policy = policy;
: previous_(GetCurrentYieldPolicy()) {
SetCurrentYieldPolicy(policy);
}
ScopedYieldPolicy::~ScopedYieldPolicy() {
current_yield_policy = previous_;
SetCurrentYieldPolicy(previous_);
}
void ScopedYieldPolicy::YieldExecution() {
if (current_yield_policy)
current_yield_policy->YieldExecution();
YieldInterface* current = GetCurrentYieldPolicy();
if (current)
current->YieldExecution();
}
} // namespace rtc