tvl-depot/absl/synchronization/internal/per_thread_sem.h

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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.
//
// PerThreadSem is a low-level synchronization primitive controlling the
// runnability of a single thread, used internally by Mutex and CondVar.
//
// This is NOT a general-purpose synchronization mechanism, and should not be
// used directly by applications. Applications should use Mutex and CondVar.
//
// The semantics of PerThreadSem are the same as that of a counting semaphore.
// Each thread maintains an abstract "count" value associated with its identity.
#ifndef ABSL_SYNCHRONIZATION_INTERNAL_PER_THREAD_SEM_H_
#define ABSL_SYNCHRONIZATION_INTERNAL_PER_THREAD_SEM_H_
#include <atomic>
#include "absl/base/internal/thread_identity.h"
#include "absl/synchronization/internal/create_thread_identity.h"
#include "absl/synchronization/internal/kernel_timeout.h"
namespace absl {
Export of internal Abseil changes -- c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro <dmauro@google.com>: Remove a floating point division by zero test. This isn't testing behavior related to the library, and MSVC warns about it in opt mode. PiperOrigin-RevId: 285220804 -- 68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental <rogeeff@google.com>: This CL introduces following changes to the class FlagImpl: * We eliminate the CommandLineFlagLocks struct. Instead callback guard and callback function are combined into a single CallbackData struct, while primary data lock is stored separately. * CallbackData member of class FlagImpl is initially set to be nullptr and is only allocated and initialized when a flag's callback is being set. For most flags we do not pay for the extra space and extra absl::Mutex now. * Primary data guard is stored in data_guard_ data member. This is a properly aligned character buffer of necessary size. During initialization of the flag we construct absl::Mutex in this space using placement new call. * We now avoid extra value copy after successful attempt to parse value out of string. Instead we swap flag's current value with tentative value we just produced. PiperOrigin-RevId: 285132636 -- ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck <shreck@google.com>: Change null-term* (and nul-term*) to NUL-term* in comments PiperOrigin-RevId: 285036610 -- 729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro <dmauro@google.com>: Use the Posix implementation of thread identity on MinGW. Some versions of MinGW suffer from thread_local bugs. PiperOrigin-RevId: 285022920 -- 39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon <gfalcon@google.com>: Implementation detail change. Add further ABSL_NAMESPACE_BEGIN and _END annotation macros to files in Abseil. PiperOrigin-RevId: 285012012 GitOrigin-RevId: c99f979ad34f155fbeeea69b88bdc7458d89a21c Change-Id: I4c85d3704e45d11a9ac50d562f39640a6adbedc1
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ABSL_NAMESPACE_BEGIN
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class Mutex;
namespace synchronization_internal {
class PerThreadSem {
public:
PerThreadSem() = delete;
PerThreadSem(const PerThreadSem&) = delete;
PerThreadSem& operator=(const PerThreadSem&) = delete;
// Routine invoked periodically (once a second) by a background thread.
// Has no effect on user-visible state.
static void Tick(base_internal::ThreadIdentity* identity);
// ---------------------------------------------------------------------------
// Routines used by autosizing threadpools to detect when threads are
// blocked. Each thread has a counter pointer, initially zero. If non-zero,
// the implementation atomically increments the counter when it blocks on a
// semaphore, a decrements it again when it wakes. This allows a threadpool
// to keep track of how many of its threads are blocked.
// SetThreadBlockedCounter() should be used only by threadpool
// implementations. GetThreadBlockedCounter() should be used by modules that
// block threads; if the pointer returned is non-zero, the location should be
// incremented before the thread blocks, and decremented after it wakes.
static void SetThreadBlockedCounter(std::atomic<int> *counter);
static std::atomic<int> *GetThreadBlockedCounter();
private:
// Create the PerThreadSem associated with "identity". Initializes count=0.
// REQUIRES: May only be called by ThreadIdentity.
static void Init(base_internal::ThreadIdentity* identity);
Export of internal Abseil changes -- 90ecacd2a3db96ee64ef23af37a80fad404e2b32 by Gennadiy Rozental <rogeeff@google.com>: Fixes MSVC regression by making MSVC version of class Flag into an aggregate type. PiperOrigin-RevId: 277767054 -- 018f3b040df51d91a988fa146fee163721e605e9 by Abseil Team <absl-team@google.com>: Change libstdc++ lacking std::unique_ptr check from a gcc version check to based on feature macros. PiperOrigin-RevId: 277736042 -- 475844775ae343e2414318f08549ee3fa6676a8d by CJ Johnson <johnsoncj@google.com>: Pass allocator_type through allocator_traits before extracting the typedefs PiperOrigin-RevId: 277730393 -- d843bc4bc30bf5b11af76db8beda8634b6111a62 by Abseil Team <absl-team@google.com>: Convert the Waiter::Init() method to the default constructor and define a destructor for the Waiter class. Use placement new and delete with Waiter objects. PiperOrigin-RevId: 277728823 -- 1ba6edf421dd2dfe13c55970a03c99592cb6677d by Derek Mauro <dmauro@google.com>: Use lowercase spelling for include of dbghelp.h When cross-compiling under MinGW this is important PiperOrigin-RevId: 277629783 -- cfc662a6fa357a84ddda8037156c7f26cee40c36 by Abseil Team <absl-team@google.com>: Don't use atomic ops on waiter and wakeup counts in WIN32 waiter mode. Port the new CONDVAR waiter mode code in CL 277366017 to the WIN32 waiter mode. PiperOrigin-RevId: 277603611 -- 833106542e61fa0832900adf3c1b2afc6890b94b by Abseil Team <absl-team@google.com>: Add the PerThreadSem::Destroy() method. For ABSL_WAITER_MODE_CONDVAR or ABSL_WAITER_MODE_SEM, PerThreadSem::Destroy() is used to destroy the pthread mutex and condition variable or the POSIX semaphore. PiperOrigin-RevId: 277586675 -- 7814da4a59106cf1e0e4db1a31b9592ebbd2094b by Samuel Benzaquen <sbenza@google.com>: Enable the assertion in the iterator's operator* and operator-> PiperOrigin-RevId: 277563401 GitOrigin-RevId: 90ecacd2a3db96ee64ef23af37a80fad404e2b32 Change-Id: Ib19be3680da74f0b94055c9039115ec6bcaea7b0
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// Destroy the PerThreadSem associated with "identity".
// REQUIRES: May only be called by ThreadIdentity.
static void Destroy(base_internal::ThreadIdentity* identity);
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// Increments "identity"'s count.
static inline void Post(base_internal::ThreadIdentity* identity);
// Waits until either our count > 0 or t has expired.
// If count > 0, decrements count and returns true. Otherwise returns false.
// !t.has_timeout() => Wait(t) will return true.
static inline bool Wait(KernelTimeout t);
// White-listed callers.
friend class PerThreadSemTest;
friend class absl::Mutex;
friend absl::base_internal::ThreadIdentity* CreateThreadIdentity();
Export of internal Abseil changes -- 90ecacd2a3db96ee64ef23af37a80fad404e2b32 by Gennadiy Rozental <rogeeff@google.com>: Fixes MSVC regression by making MSVC version of class Flag into an aggregate type. PiperOrigin-RevId: 277767054 -- 018f3b040df51d91a988fa146fee163721e605e9 by Abseil Team <absl-team@google.com>: Change libstdc++ lacking std::unique_ptr check from a gcc version check to based on feature macros. PiperOrigin-RevId: 277736042 -- 475844775ae343e2414318f08549ee3fa6676a8d by CJ Johnson <johnsoncj@google.com>: Pass allocator_type through allocator_traits before extracting the typedefs PiperOrigin-RevId: 277730393 -- d843bc4bc30bf5b11af76db8beda8634b6111a62 by Abseil Team <absl-team@google.com>: Convert the Waiter::Init() method to the default constructor and define a destructor for the Waiter class. Use placement new and delete with Waiter objects. PiperOrigin-RevId: 277728823 -- 1ba6edf421dd2dfe13c55970a03c99592cb6677d by Derek Mauro <dmauro@google.com>: Use lowercase spelling for include of dbghelp.h When cross-compiling under MinGW this is important PiperOrigin-RevId: 277629783 -- cfc662a6fa357a84ddda8037156c7f26cee40c36 by Abseil Team <absl-team@google.com>: Don't use atomic ops on waiter and wakeup counts in WIN32 waiter mode. Port the new CONDVAR waiter mode code in CL 277366017 to the WIN32 waiter mode. PiperOrigin-RevId: 277603611 -- 833106542e61fa0832900adf3c1b2afc6890b94b by Abseil Team <absl-team@google.com>: Add the PerThreadSem::Destroy() method. For ABSL_WAITER_MODE_CONDVAR or ABSL_WAITER_MODE_SEM, PerThreadSem::Destroy() is used to destroy the pthread mutex and condition variable or the POSIX semaphore. PiperOrigin-RevId: 277586675 -- 7814da4a59106cf1e0e4db1a31b9592ebbd2094b by Samuel Benzaquen <sbenza@google.com>: Enable the assertion in the iterator's operator* and operator-> PiperOrigin-RevId: 277563401 GitOrigin-RevId: 90ecacd2a3db96ee64ef23af37a80fad404e2b32 Change-Id: Ib19be3680da74f0b94055c9039115ec6bcaea7b0
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friend void ReclaimThreadIdentity(void* v);
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};
} // namespace synchronization_internal
Export of internal Abseil changes -- c99f979ad34f155fbeeea69b88bdc7458d89a21c by Derek Mauro <dmauro@google.com>: Remove a floating point division by zero test. This isn't testing behavior related to the library, and MSVC warns about it in opt mode. PiperOrigin-RevId: 285220804 -- 68b015491f0dbf1ab547994673281abd1f34cd4b by Gennadiy Rozental <rogeeff@google.com>: This CL introduces following changes to the class FlagImpl: * We eliminate the CommandLineFlagLocks struct. Instead callback guard and callback function are combined into a single CallbackData struct, while primary data lock is stored separately. * CallbackData member of class FlagImpl is initially set to be nullptr and is only allocated and initialized when a flag's callback is being set. For most flags we do not pay for the extra space and extra absl::Mutex now. * Primary data guard is stored in data_guard_ data member. This is a properly aligned character buffer of necessary size. During initialization of the flag we construct absl::Mutex in this space using placement new call. * We now avoid extra value copy after successful attempt to parse value out of string. Instead we swap flag's current value with tentative value we just produced. PiperOrigin-RevId: 285132636 -- ed45d118fb818969eb13094cf7827c885dfc562c by Tom Manshreck <shreck@google.com>: Change null-term* (and nul-term*) to NUL-term* in comments PiperOrigin-RevId: 285036610 -- 729619017944db895ce8d6d29c1995aa2e5628a5 by Derek Mauro <dmauro@google.com>: Use the Posix implementation of thread identity on MinGW. Some versions of MinGW suffer from thread_local bugs. PiperOrigin-RevId: 285022920 -- 39a25493503c76885bc3254c28f66a251c5b5bb0 by Greg Falcon <gfalcon@google.com>: Implementation detail change. Add further ABSL_NAMESPACE_BEGIN and _END annotation macros to files in Abseil. PiperOrigin-RevId: 285012012 GitOrigin-RevId: c99f979ad34f155fbeeea69b88bdc7458d89a21c Change-Id: I4c85d3704e45d11a9ac50d562f39640a6adbedc1
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ABSL_NAMESPACE_END
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} // namespace absl
// In some build configurations we pass --detect-odr-violations to the
// gold linker. This causes it to flag weak symbol overrides as ODR
// violations. Because ODR only applies to C++ and not C,
// --detect-odr-violations ignores symbols not mangled with C++ names.
// By changing our extension points to be extern "C", we dodge this
// check.
extern "C" {
void AbslInternalPerThreadSemPost(
absl::base_internal::ThreadIdentity* identity);
bool AbslInternalPerThreadSemWait(
absl::synchronization_internal::KernelTimeout t);
} // extern "C"
void absl::synchronization_internal::PerThreadSem::Post(
absl::base_internal::ThreadIdentity* identity) {
AbslInternalPerThreadSemPost(identity);
}
bool absl::synchronization_internal::PerThreadSem::Wait(
absl::synchronization_internal::KernelTimeout t) {
return AbslInternalPerThreadSemWait(t);
}
Export of internal Abseil changes. -- bdce7e57e9e886eff1114d0266781b443f7ec639 by Derek Mauro <dmauro@google.com>: Change {Get|Set}EnvironmentVariable to {Get|Set}EnvironmentVariableA for compatibility with /DUNICODE. PiperOrigin-RevId: 239229514 -- 2276ed502326a044a84060d34eb19d499e3a3be2 by Derek Mauro <dmauro@google.com>: Import of CCTZ from GitHub. PiperOrigin-RevId: 239228622 -- a462efb970ff43b08a362ef2343fb75ac1295a50 by Derek Mauro <dmauro@google.com>: Adding linking of CoreFoundation to CMakeLists in absl/time. Import https://github.com/abseil/abseil-cpp/pull/280. Fix #283 PiperOrigin-RevId: 239220785 -- fc23327b97f940c682aae1956cf7a1bf87f88c06 by Derek Mauro <dmauro@google.com>: Add hermetic test script that uses Docker to build with a very recent version of gcc (8.3.0 today) with libstdc++ and bazel. PiperOrigin-RevId: 239220448 -- 418c08a8f6a53e63b84e39473035774417ca3aa7 by Derek Mauro <dmauro@google.com>: Disable part of the variant exeception safety test on move assignment when using versions of libstd++ that contain a bug. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87431#c7 PiperOrigin-RevId: 239062455 -- 799722217aeda79679577843c91d5be62cbcbb42 by Matt Calabrese <calabrese@google.com>: Add internal-only IsSwappable traits corresponding to std::is_swappable and std::is_nothrow_swappable, which are used with the swap implementations of optional and variant. PiperOrigin-RevId: 239049448 -- aa46a036038a3de5c68ac5e5d3b4bf76f818d2ea by CJ Johnson <johnsoncj@google.com>: Make InlinedVectorStorage constructor explicit PiperOrigin-RevId: 239044361 -- 17949715b3aa21c794701f69f2154e91b6acabc3 by CJ Johnson <johnsoncj@google.com>: Add absl namesapce to internal/inlined_vector.h PiperOrigin-RevId: 239030789 -- 834628325953078cc08ed10d23bb8890e5bec897 by Derek Mauro <dmauro@google.com>: Add test script that uses Docker to build Abseil with gcc-4.8, libstdc++, and cmake. PiperOrigin-RevId: 239028433 -- 80fe24149ed73ed2ced995ad1e372fb060c60427 by CJ Johnson <johnsoncj@google.com>: Factors data members of InlinedVector into an impl type called InlinedVectorStorage so that (in future changes) the contents of a vector can be grouped together with a single pointer. PiperOrigin-RevId: 239021086 -- 585331436d5d4d79f845e45dcf79d918a0dc6169 by Derek Mauro <dmauro@google.com>: Add -Wno-missing-field-initializers to gcc compiler flags. gcc-4.x has spurious missing field initializer warnings. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36750 PiperOrigin-RevId: 239017217 -- 94602fe4e33ee3a552a7f2939c0f57a992f55075 by Abseil Team <absl-team@google.com>: Formatting fixes. PiperOrigin-RevId: 238983038 -- a1c1b63c08505574e0a8c491561840cecb2bb93e by Derek Mauro <dmauro@google.com>: Add hermetic test script that uses Docker to build with a very recent version of clang with libc++ and bazel. PiperOrigin-RevId: 238669118 -- e525f8d20bc2f79a0d69336b902f63858f3bff9d by Derek Mauro <dmauro@google.com>: Disable the test optionalTest.InPlaceTSFINAEBug until libc++ is updated. PiperOrigin-RevId: 238661703 -- f99a2a0b5ec424a059678f7f226600f137b4c74e by Derek Mauro <dmauro@google.com>: Correct the check for the FlatHashMap-Any test bug (list conditions instead of platforms when possible) PiperOrigin-RevId: 238653344 -- 777928035dbcbf39f361eb7d10dc3696822f692f by Jon Cohen <cohenjon@google.com>: Add install rules for Abseil CMake. These are attempted to be limited to in-project installation. This serves two purposes -- first it's morally the same as using Abseil in-source, except you don't have to rebuild us every time. Second, the presence of an install rule makes life massively simpler for package manager maintainers. Currently this doesn't install absl tests or testonly libraries. This can be added in a follow-up patch. Fixes #38, Fixes #80, Closes #182 PiperOrigin-RevId: 238645836 -- ded1c6ce697c191b7a6ff14572b3e6d183117b2c by Derek Mauro <dmauro@google.com>: Add hermetic test script that uses Docker to build with a very recent version of clang with libstdc++ and bazel. PiperOrigin-RevId: 238517815 GitOrigin-RevId: bdce7e57e9e886eff1114d0266781b443f7ec639 Change-Id: I6f745869cb8ef63851891ccac05ae9a7dd241c4f
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#endif // ABSL_SYNCHRONIZATION_INTERNAL_PER_THREAD_SEM_H_