|
|
|
// 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.
|
|
|
|
|
|
|
|
#include <stdint.h>
|
|
|
|
#include <new>
|
|
|
|
|
|
|
|
// 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"
|
|
|
|
#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 void ResetThreadIdentity(base_internal::ThreadIdentity* identity) {
|
|
|
|
base_internal::PerThreadSynch* pts = &identity->per_thread_synch;
|
|
|
|
pts->next = nullptr;
|
|
|
|
pts->skip = nullptr;
|
|
|
|
pts->may_skip = false;
|
|
|
|
pts->waitp = nullptr;
|
|
|
|
pts->suppress_fatal_errors = false;
|
|
|
|
pts->readers = 0;
|
|
|
|
pts->priority = 0;
|
|
|
|
pts->next_priority_read_cycles = 0;
|
|
|
|
pts->state.store(base_internal::PerThreadSynch::State::kAvailable,
|
|
|
|
std::memory_order_relaxed);
|
|
|
|
pts->maybe_unlocking = false;
|
|
|
|
pts->wake = false;
|
|
|
|
pts->cond_waiter = false;
|
|
|
|
pts->all_locks = nullptr;
|
|
|
|
identity->waiter_state = {};
|
|
|
|
identity->blocked_count_ptr = nullptr;
|
|
|
|
identity->ticker.store(0, std::memory_order_relaxed);
|
|
|
|
identity->wait_start.store(0, std::memory_order_relaxed);
|
|
|
|
identity->is_idle.store(false, std::memory_order_relaxed);
|
|
|
|
identity->next = nullptr;
|
|
|
|
}
|
|
|
|
|
|
|
|
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));
|
|
|
|
}
|
|
|
|
ResetThreadIdentity(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
|