thread_identity.cc | Explore in Territory

// 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
//
// 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"

#if !defined(_WIN32) || defined(__MINGW32__)
#include <pthread.h>
#ifndef __wasi__
// WASI does not provide this header, either way we disable use
// of signals with it below.
#include <signal.h>
#endif
#endif

#include <atomic>
#include <cassert>
#include <memory>

#include "absl/base/attributes.h"
#include "absl/base/call_once.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/internal/spinlock.h"

namespace absl {
ABSL_NAMESPACE_BEGIN
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) { … }
}  // 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.
// "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.
// Apple platforms have the visibility attribute, but issue a compile warning
// that protected visibility is unsupported.
ABSL_CONST_INIT  // Must come before __attribute__((visibility("protected")))
#if ABSL_HAVE_ATTRIBUTE(visibility) && !defined(__APPLE__)
    __attribute__((visibility("protected")))
#endif  // ABSL_HAVE_ATTRIBUTE(visibility) && !defined(__APPLE__)
#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
#endif  // TLS or CPP11

void SetCurrentThreadIdentity(ThreadIdentity* identity,
                              ThreadIdentityReclaimerFunction reclaimer) { … }

#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS || \
    ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_CPP11

// Please see the comment on `CurrentThreadIdentityIfPresent` in
// thread_identity.h. When we cannot expose thread_local variables in
// headers, we opt for the correct-but-slower option of not inlining this
// function.
#ifndef ABSL_INTERNAL_INLINE_CURRENT_THREAD_IDENTITY_IF_PRESENT
ThreadIdentity* CurrentThreadIdentityIfPresent() { return thread_identity_ptr; }
#endif
#endif

void ClearCurrentThreadIdentity() { … }

#if ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_POSIX_SETSPECIFIC
ThreadIdentity* CurrentThreadIdentityIfPresent() { … }
#endif

}  // namespace base_internal
ABSL_NAMESPACE_END
}  // namespace absl
chromium/third_party/abseil-cpp/absl/base/internal/thread_identity.cc
