tvl-depot/absl/base/internal/thread_identity.cc

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// Copyright 2017 The Abseil Authors.
//
// 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
//
// https://www.apache.org/licenses/LICENSE-2.0
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//
// 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.
#include "absl/base/internal/thread_identity.h"
#ifndef _WIN32
#include <pthread.h>
#include <signal.h>
#endif
#include <atomic>
#include <cassert>
#include <memory>
#include "absl/base/call_once.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/internal/spinlock.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
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namespace base_internal {
#if ABSL_THREAD_IDENTITY_MODE != ABSL_THREAD_IDENTITY_MODE_USE_CPP11
namespace {
// Used to co-ordinate one-time creation of our pthread_key
absl::once_flag init_thread_identity_key_once;
pthread_key_t thread_identity_pthread_key;
std::atomic<bool> pthread_key_initialized(false);
void AllocateThreadIdentityKey(ThreadIdentityReclaimerFunction reclaimer) {
pthread_key_create(&thread_identity_pthread_key, reclaimer);
pthread_key_initialized.store(true, std::memory_order_release);
}
} // namespace
#endif
#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS || \
ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11
// The actual TLS storage for a thread's currently associated ThreadIdentity.
// This is referenced by inline accessors in the header.
Changes imported from Abseil "staging" branch: - b527a3e4b36b644ac424e3c525b1cd393f6f6c40 Fix some typos in the usage examples by Jorg Brown <jorg@google.com> - 82be4a9adf3bb0ddafc0d46274969c99afffe870 Fix typo in optional.h comment. by Abseil Team <absl-team@google.com> - d6ee63bf8fc51fba074c23b33cebc28c808d7f07 Remove internal-only identifiers from code. by Daniel Katz <katzdm@google.com> - f9c3ad2f0d73f53b21603638af8b4bed636e79f4 Use easier understandable names for absl::StartsWith and ... by Abseil Team <absl-team@google.com> - 7c16c14fefee89c927b8789d6043c4691bcffc9b Add -Wno-missing-prototypes back to the LLVM copts. by Derek Mauro <dmauro@google.com> - 2f4b7d2e50c7023240242f1e15db60ccd7e8768d IWYU | absl/strings by Juemin Yang <jueminyang@google.com> - a99cbcc1daa34a2d6a2bb26de275e05173cc77e9 IWYU | absl/type by Juemin Yang <jueminyang@google.com> - 12e1146d0fc76c071d7e0ebaabb62f0a984fae66 Use LLVM_FLAGS and LLVM_TEST_FLAGS when --compiler=llvm. by Derek Mauro <dmauro@google.com> - cd6bea616abda558d0bace5bd77455662a233688 IWYU | absl/debugging by Juemin Yang <jueminyang@google.com> - d9a7382e59d46a8581b6b7a31cd5a48bb89326e9 IWYU | absl/synchronization by Juemin Yang <jueminyang@google.com> - 07ec7d6d5a4a666f4183c5d0ed9c342baa7b24bc IWYU | absl/numeric by Juemin Yang <jueminyang@google.com> - 12bfe40051f4270f8707e191af5652f83f2f750c Remove the RoundTrip{Float,Double}ToBuffer routines from ... by Jorg Brown <jorg@google.com> - eeb4fd67c9d97f66cb9475c3c5e51ab132f1c810 Adds conversion functions for converting between absl/tim... by Greg Miller <jgm@google.com> - 59a2108d05d4ea85dc5cc11e49b2cd2335d4295a Change Substitute to use %.6g formatting rather than 15/1... by Jorg Brown <jorg@google.com> - 394becb48e0fcd161642cdaac5120d32567e0ef8 IWYU | absl/meta by Juemin Yang <jueminyang@google.com> - 1e5da6e8da336699b2469dcf6dda025b9b0ec4c9 Rewrite atomic_hook.h to not use std::atomic<T*> under Wi... by Greg Falcon <gfalcon@google.com> GitOrigin-RevId: b527a3e4b36b644ac424e3c525b1cd393f6f6c40 Change-Id: I14e331d91c956ef045ac7927091a9f179716de0c
2017-09-24 17:20:48 +02:00
// "protected" visibility ensures that if multiple instances of Abseil code
// exist within a process (via dlopen() or similar), references to
// thread_identity_ptr from each instance of the code will refer to
// *different* instances of this ptr.
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#ifdef __GNUC__
__attribute__((visibility("protected")))
#endif // __GNUC__
#if ABSL_PER_THREAD_TLS
// Prefer __thread to thread_local as benchmarks indicate it is a bit faster.
ABSL_PER_THREAD_TLS_KEYWORD ThreadIdentity* thread_identity_ptr = nullptr;
#elif defined(ABSL_HAVE_THREAD_LOCAL)
thread_local ThreadIdentity* thread_identity_ptr = nullptr;
#endif // ABSL_PER_THREAD_TLS
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#endif // TLS or CPP11
void SetCurrentThreadIdentity(
ThreadIdentity* identity, ThreadIdentityReclaimerFunction reclaimer) {
assert(CurrentThreadIdentityIfPresent() == nullptr);
// Associate our destructor.
// NOTE: This call to pthread_setspecific is currently the only immovable
// barrier to CurrentThreadIdentity() always being async signal safe.
#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
// NOTE: Not async-safe. But can be open-coded.
absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey,
reclaimer);
#if defined(__EMSCRIPTEN__) || defined(__MINGW32__)
// Emscripten and MinGW pthread implementations does not support signals.
// See https://kripken.github.io/emscripten-site/docs/porting/pthreads.html
// for more information.
pthread_setspecific(thread_identity_pthread_key,
reinterpret_cast<void*>(identity));
#else
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// We must mask signals around the call to setspecific as with current glibc,
// a concurrent getspecific (needed for GetCurrentThreadIdentityIfPresent())
// may zero our value.
//
// While not officially async-signal safe, getspecific within a signal handler
// is otherwise OK.
sigset_t all_signals;
sigset_t curr_signals;
sigfillset(&all_signals);
pthread_sigmask(SIG_SETMASK, &all_signals, &curr_signals);
pthread_setspecific(thread_identity_pthread_key,
reinterpret_cast<void*>(identity));
pthread_sigmask(SIG_SETMASK, &curr_signals, nullptr);
#endif // !__EMSCRIPTEN__ && !__MINGW32__
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#elif ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS
// NOTE: Not async-safe. But can be open-coded.
absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey,
reclaimer);
pthread_setspecific(thread_identity_pthread_key,
reinterpret_cast<void*>(identity));
thread_identity_ptr = identity;
#elif ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11
thread_local std::unique_ptr<ThreadIdentity, ThreadIdentityReclaimerFunction>
holder(identity, reclaimer);
thread_identity_ptr = identity;
#else
#error Unimplemented ABSL_THREAD_IDENTITY_MODE
#endif
}
void ClearCurrentThreadIdentity() {
#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS || \
ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11
thread_identity_ptr = nullptr;
#elif ABSL_THREAD_IDENTITY_MODE == \
ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
// pthread_setspecific expected to clear value on destruction
assert(CurrentThreadIdentityIfPresent() == nullptr);
#endif
}
#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
ThreadIdentity* CurrentThreadIdentityIfPresent() {
bool initialized = pthread_key_initialized.load(std::memory_order_acquire);
if (!initialized) {
return nullptr;
}
return reinterpret_cast<ThreadIdentity*>(
pthread_getspecific(thread_identity_pthread_key));
}
#endif
} // namespace base_internal
ABSL_NAMESPACE_END
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} // namespace absl