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/*
* Copyright (C) 2008 Apple Inc. All rights reserved.
* Copyright (C) 2009 Jian Li <jianli@chromium.org>
* Copyright (C) 2012 Patrick Gansterer <paroga@paroga.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_THREAD_SPECIFIC_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_THREAD_SPECIFIC_H_
#include "base/threading/thread_local_storage.h"
#include "build/build_config.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/allocator/partition_allocator.h"
#include "third_party/blink/renderer/platform/wtf/allocator/partitions.h"
#include "third_party/blink/renderer/platform/wtf/stack_util.h"
#include "third_party/blink/renderer/platform/wtf/wtf.h"
#include "third_party/blink/renderer/platform/wtf/wtf_export.h"
namespace WTF {
template <typename T>
class ThreadSpecific {
USING_FAST_MALLOC(ThreadSpecific);
public:
ThreadSpecific() : slot_(&Destroy) {}
ThreadSpecific(const ThreadSpecific&) = delete;
ThreadSpecific& operator=(const ThreadSpecific&) = delete;
bool
IsSet(); // Useful as a fast check to see if this thread has set this value.
T* operator->();
operator T*();
T& operator*();
private:
// Not implemented. It's technically possible to destroy a thread specific
// key, but one would need to make sure that all values have been destroyed
// already (usually, that all threads that used it have exited). It's
// unlikely that any user of this call will be in that situation - and having
// a destructor defined can be confusing, given that it has such strong
// pre-requisites to work correctly.
~ThreadSpecific() = delete;
T* Get() { return static_cast<T*>(slot_.Get()); }
void Set(T* ptr) {
DCHECK(!Get());
slot_.Set(ptr);
}
void static Destroy(void* ptr);
// This member must only be accessed or modified on the main thread.
T* main_thread_storage_ = nullptr;
base::ThreadLocalStorage::Slot slot_;
};
template <typename T>
inline void ThreadSpecific<T>::Destroy(void* ptr) {
// Never call destructors on the main thread. This is fine because Blink no
// longer has a graceful shutdown sequence. Be careful to call this function
// (which can be re-entrant) while the pointer is still set, to avoid lazily
// allocating Threading after it is destroyed.
if (IsMainThread())
return;
// The memory was allocated via Partitions::FastZeroedMalloc, and then the
// object was placement-newed. To destroy, we must call the delete expression,
// and then free the memory manually.
T* instance = static_cast<T*>(ptr);
instance->~T();
Partitions::FastFree(ptr);
}
template <typename T>
inline bool ThreadSpecific<T>::IsSet() {
return !!Get();
}
template <typename T>
inline ThreadSpecific<T>::operator T*() {
T* off_thread_ptr;
#if defined(__GLIBC__) || BUILDFLAG(IS_ANDROID) || BUILDFLAG(IS_FREEBSD)
// TLS is fast on these platforms.
// TODO(csharrison): Qualify this statement for Android.
const bool kMainThreadAlwaysChecksTLS = true;
T** ptr = &off_thread_ptr;
off_thread_ptr = static_cast<T*>(Get());
#else
const bool kMainThreadAlwaysChecksTLS = false;
T** ptr = &main_thread_storage_;
if (MayNotBeMainThread()) [[unlikely]] {
off_thread_ptr = static_cast<T*>(Get());
ptr = &off_thread_ptr;
}
#endif
// Set up thread-specific value's memory pointer before invoking constructor,
// in case any function it calls needs to access the value, to avoid
// recursion.
if (!*ptr) [[unlikely]] {
*ptr = static_cast<T*>(Partitions::FastZeroedMalloc(
sizeof(T), WTF_HEAP_PROFILER_TYPE_NAME(T)));
// Even if we didn't realize we're on the main thread, we might still be.
// We need to double-check so that |main_thread_storage_| is populated.
if (!kMainThreadAlwaysChecksTLS && ptr != &main_thread_storage_ &&
IsMainThread()) [[unlikely]] {
main_thread_storage_ = *ptr;
}
Set(*ptr);
::new (NotNullTag::kNotNull, *ptr) T;
}
return *ptr;
}
template <typename T>
inline T* ThreadSpecific<T>::operator->() {
return operator T*();
}
template <typename T>
inline T& ThreadSpecific<T>::operator*() {
return *operator T*();
}
} // namespace WTF
using WTF::ThreadSpecific;
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_THREAD_SPECIFIC_H_
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