tvl-depot/absl/synchronization/internal/create_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
//
// http://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.
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
#include <stdint.h>
#include <new>
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// This file is a no-op if the required LowLevelAlloc support is missing.
#include "absl/base/internal/low_level_alloc.h"
#ifndef ABSL_LOW_LEVEL_ALLOC_MISSING
#include <string.h>
#include "absl/base/attributes.h"
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#include "absl/base/internal/spinlock.h"
#include "absl/base/internal/thread_identity.h"
#include "absl/synchronization/internal/per_thread_sem.h"
namespace absl {
namespace synchronization_internal {
// ThreadIdentity storage is persistent, we maintain a free-list of previously
// released ThreadIdentity objects.
static base_internal::SpinLock freelist_lock(base_internal::kLinkerInitialized);
static base_internal::ThreadIdentity* thread_identity_freelist;
// A per-thread destructor for reclaiming associated ThreadIdentity objects.
// Since we must preserve their storage we cache them for re-use.
static void ReclaimThreadIdentity(void* v) {
base_internal::ThreadIdentity* identity =
static_cast<base_internal::ThreadIdentity*>(v);
// all_locks might have been allocated by the Mutex implementation.
// We free it here when we are notified that our thread is dying.
if (identity->per_thread_synch.all_locks != nullptr) {
base_internal::LowLevelAlloc::Free(identity->per_thread_synch.all_locks);
}
// We must explicitly clear the current thread's identity:
// (a) Subsequent (unrelated) per-thread destructors may require an identity.
// We must guarantee a new identity is used in this case (this instructor
// will be reinvoked up to PTHREAD_DESTRUCTOR_ITERATIONS in this case).
// (b) ThreadIdentity implementations may depend on memory that is not
// reinitialized before reuse. We must allow explicit clearing of the
// association state in this case.
base_internal::ClearCurrentThreadIdentity();
{
base_internal::SpinLockHolder l(&freelist_lock);
identity->next = thread_identity_freelist;
thread_identity_freelist = identity;
}
}
// Return value rounded up to next multiple of align.
// Align must be a power of two.
static intptr_t RoundUp(intptr_t addr, intptr_t align) {
return (addr + align - 1) & ~(align - 1);
}
static base_internal::ThreadIdentity* NewThreadIdentity() {
base_internal::ThreadIdentity* identity = nullptr;
{
// Re-use a previously released object if possible.
base_internal::SpinLockHolder l(&freelist_lock);
if (thread_identity_freelist) {
identity = thread_identity_freelist; // Take list-head.
thread_identity_freelist = thread_identity_freelist->next;
}
}
if (identity == nullptr) {
// Allocate enough space to align ThreadIdentity to a multiple of
// PerThreadSynch::kAlignment. This space is never released (it is
// added to a freelist by ReclaimThreadIdentity instead).
void* allocation = base_internal::LowLevelAlloc::Alloc(
sizeof(*identity) + base_internal::PerThreadSynch::kAlignment - 1);
// Round up the address to the required alignment.
identity = reinterpret_cast<base_internal::ThreadIdentity*>(
RoundUp(reinterpret_cast<intptr_t>(allocation),
base_internal::PerThreadSynch::kAlignment));
}
memset(identity, 0, sizeof(*identity));
return identity;
}
// Allocates and attaches ThreadIdentity object for the calling thread. Returns
// the new identity.
// REQUIRES: CurrentThreadIdentity(false) == nullptr
base_internal::ThreadIdentity* CreateThreadIdentity() {
base_internal::ThreadIdentity* identity = NewThreadIdentity();
PerThreadSem::Init(identity);
// Associate the value with the current thread, and attach our destructor.
base_internal::SetCurrentThreadIdentity(identity, ReclaimThreadIdentity);
return identity;
}
} // namespace synchronization_internal
} // namespace absl
#endif // ABSL_LOW_LEVEL_ALLOC_MISSING