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
}
Export of internal Abseil changes -- 8bdb2020150ed0fd4a4e520e454dc5f54e33f776 by Eric Fiselier <ericwf@google.com>: Workaround bug in GCC 9.2 and after. PiperOrigin-RevId: 291982551 -- 47ff4820e595f96c082a90d733725f6882d83e3b by Abseil Team <absl-team@google.com>: Improve ABSL_ATTRIBUTE_PACKED documentation Recommend to apply ABSL_ATTRIBUTE_PACKED to structure members instead of to an entire structure because applying this attribute to an entire structure may cause the compiler to generate suboptimal code. It reduces the alignment of the data structure from a value larger than one to one. When applied to a structure, ABSL_ATTRIBUTE_PACKED reduces the alignment of a structure (alignof()) to 1. As a result, the compiler can no longer assume that e.g. uint32 members are aligned on a four byte boundary and hence is forced to use single-byte load and store instructions on CPU architectures that do not support non-aligned loads or stores. PiperOrigin-RevId: 291977920 -- 902b7a86f860da699d3a2e5c738be5ef73ede3b4 by Mark Barolak <mbar@google.com>: Internal change PiperOrigin-RevId: 291963048 -- bb3bd3247e376d53a3080b105f13ec7566d3ae50 by Abseil Team <absl-team@google.com>: Support the C++17 insert_or_assign() API in btree_map. PiperOrigin-RevId: 291945474 -- ff3b3cfcbbc64f086f95501f48d49426bcde356f by Gennadiy Rozental <rogeeff@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 291861110 -- fd465cd9cbbacd3962f67a7346d6462edaddd809 by Derek Mauro <dmauro@google.com>: Add flaky=1 to beta_distribution_test. PiperOrigin-RevId: 291757364 -- 3603adfb59c4128c542b670952cce250d59e1f67 by Derek Mauro <dmauro@google.com>: Separate the initialization of NumCPUs() and NominalCPUFrequency() The OSS version of Abseil never needs to call NominalCPUFrequency(). In some configurations, initializing NominalCPUFrequency() requires spending at least 3ms measuring the CPU frequency. By separating the initialization from NumCPUs(), which is called in most configurations, we can save at least 3ms of program startup time. PiperOrigin-RevId: 291737273 -- bea9e4a6bff5a0351d340deab966641867e08c4d by Abseil Team <absl-team@google.com>: Change the cmake library names not to have a redundant `absl_` prefix. PiperOrigin-RevId: 291640501 -- 501b602ef260cd7c8c527342581ceffb3c5b6d4c by Gennadiy Rozental <rogeeff@google.com>: Introducing benchmark for absl::GetFlag. PiperOrigin-RevId: 291433394 -- 4eeaddc788da4b91c272a8adca77ca6dbbbc1d44 by Xiaoyi Zhang <zhangxy@google.com>: fix: Add support for more ARM processors detection Import of https://github.com/abseil/abseil-cpp/pull/608 PiperOrigin-RevId: 291420397 -- a3087a8e883c5d71de7d9bd4ec8f4db5142dfcf5 by Derek Mauro <dmauro@google.com>: Removes the flaky raw_hash_set prefetch test PiperOrigin-RevId: 291197079 -- aad6c2121c102ac36216e771c83227cf3e3bfd66 by Andy Soffer <asoffer@google.com>: Enable building Abseil as a DLL. This is currently experimental and unsupported. This CL does a few things: 1. Adds the ABSL_DLL macro to any class holding a static data member, or to global constants in headers. 2. Adds a whitelist of all files in the DLL and all the build targets that are conglomerated into the DLL. 3. When BUILD_SHARED_LIBS is specified, any build target that would be in the DLL still exists, but we swap out all of it's dependencies so it just depends on abseil_dll PiperOrigin-RevId: 291192055 -- 5e888cd6f2a7722805d41f872108a03a84e421c7 by Mark Barolak <mbar@google.com>: Move absl/strings/internal/escaping.{cc,h} into internal build targets. This puts absl/strings/internal/escaping.h behind a whitelist and it also resolves https://github.com/abseil/abseil-cpp/issues/604. PiperOrigin-RevId: 291173320 -- 166836d24970da87587c1728036f53f05a28f0af by Eric Fiselier <ericwf@google.com>: Internal Change. PiperOrigin-RevId: 291012718 -- 996ddb3dffda02440fa93f30ca5d71b14b688875 by Abseil Team <absl-team@google.com>: Fix shared libraries log spam for built-in types in absl::GetFlag PiperOrigin-RevId: 290772743 GitOrigin-RevId: 8bdb2020150ed0fd4a4e520e454dc5f54e33f776 Change-Id: I8bf2265dd14ebbace220a1b6b982bb5040ad2a26
2020-01-28 20:50:11 +01:00
#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. Because DLLs cannot expose thread_local variables in
// headers, we opt for the correct-but-slower option of placing the definition
// of this function only in a translation unit inside DLL.
#if defined(ABSL_BUILD_DLL) || defined(ABSL_CONSUME_DLL)
ThreadIdentity* CurrentThreadIdentityIfPresent() { return thread_identity_ptr; }
#endif
#endif
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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