Abseil Common Libraries (C++) (grcp 依赖)
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133 lines
5.0 KiB
133 lines
5.0 KiB
// Copyright 2017 The Abseil Authors. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// https://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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#include "absl/base/internal/thread_identity.h" |
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#ifndef _WIN32 |
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#include <pthread.h> |
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#include <signal.h> |
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#endif |
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#include <atomic> |
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#include <cassert> |
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#include <memory> |
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#include "absl/base/call_once.h" |
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#include "absl/base/internal/raw_logging.h" |
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#include "absl/base/internal/spinlock.h" |
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namespace absl { |
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namespace base_internal { |
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#if ABSL_THREAD_IDENTITY_MODE != ABSL_THREAD_IDENTITY_MODE_USE_CPP11 |
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namespace { |
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// Used to co-ordinate one-time creation of our pthread_key |
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absl::once_flag init_thread_identity_key_once; |
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pthread_key_t thread_identity_pthread_key; |
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std::atomic<bool> pthread_key_initialized(false); |
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void AllocateThreadIdentityKey(ThreadIdentityReclaimerFunction reclaimer) { |
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pthread_key_create(&thread_identity_pthread_key, reclaimer); |
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pthread_key_initialized.store(true, std::memory_order_release); |
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} |
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} // namespace |
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#endif |
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#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS || \ |
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ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11 |
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// The actual TLS storage for a thread's currently associated ThreadIdentity. |
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// This is referenced by inline accessors in the header. |
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// "protected" visibility ensures that if multiple instances of Abseil code |
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// exist within a process (via dlopen() or similar), references to |
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// thread_identity_ptr from each instance of the code will refer to |
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// *different* instances of this ptr. |
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#ifdef __GNUC__ |
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__attribute__((visibility("protected"))) |
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#endif // __GNUC__ |
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ABSL_PER_THREAD_TLS_KEYWORD ThreadIdentity* thread_identity_ptr; |
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#endif // TLS or CPP11 |
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void SetCurrentThreadIdentity( |
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ThreadIdentity* identity, ThreadIdentityReclaimerFunction reclaimer) { |
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assert(CurrentThreadIdentityIfPresent() == nullptr); |
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// Associate our destructor. |
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// NOTE: This call to pthread_setspecific is currently the only immovable |
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// barrier to CurrentThreadIdentity() always being async signal safe. |
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#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC |
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// NOTE: Not async-safe. But can be open-coded. |
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absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey, |
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reclaimer); |
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#ifdef __EMSCRIPTEN__ |
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// Emscripten PThread implementation does not support signals. |
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// See https://kripken.github.io/emscripten-site/docs/porting/pthreads.html |
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// for more information. |
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pthread_setspecific(thread_identity_pthread_key, |
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reinterpret_cast<void*>(identity)); |
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#else |
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// We must mask signals around the call to setspecific as with current glibc, |
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// a concurrent getspecific (needed for GetCurrentThreadIdentityIfPresent()) |
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// may zero our value. |
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// |
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// While not officially async-signal safe, getspecific within a signal handler |
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// is otherwise OK. |
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sigset_t all_signals; |
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sigset_t curr_signals; |
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sigfillset(&all_signals); |
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pthread_sigmask(SIG_SETMASK, &all_signals, &curr_signals); |
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pthread_setspecific(thread_identity_pthread_key, |
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reinterpret_cast<void*>(identity)); |
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pthread_sigmask(SIG_SETMASK, &curr_signals, nullptr); |
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#endif // !__EMSCRIPTEN__ |
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#elif ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS |
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// NOTE: Not async-safe. But can be open-coded. |
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absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey, |
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reclaimer); |
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pthread_setspecific(thread_identity_pthread_key, |
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reinterpret_cast<void*>(identity)); |
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thread_identity_ptr = identity; |
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#elif ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11 |
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thread_local std::unique_ptr<ThreadIdentity, ThreadIdentityReclaimerFunction> |
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holder(identity, reclaimer); |
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thread_identity_ptr = identity; |
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#else |
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#error Unimplemented ABSL_THREAD_IDENTITY_MODE |
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#endif |
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} |
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void ClearCurrentThreadIdentity() { |
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#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS || \ |
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ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11 |
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thread_identity_ptr = nullptr; |
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#elif ABSL_THREAD_IDENTITY_MODE == \ |
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ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC |
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// pthread_setspecific expected to clear value on destruction |
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assert(CurrentThreadIdentityIfPresent() == nullptr); |
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#endif |
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} |
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#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC |
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ThreadIdentity* CurrentThreadIdentityIfPresent() { |
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bool initialized = pthread_key_initialized.load(std::memory_order_acquire); |
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if (!initialized) { |
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return nullptr; |
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} |
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return reinterpret_cast<ThreadIdentity*>( |
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pthread_getspecific(thread_identity_pthread_key)); |
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} |
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#endif |
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} // namespace base_internal |
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} // namespace absl
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