Emilio Cobos Álvarez
a0c49d6f4f
Based on the Rust implementations: * https://github.com/rust-lang/rust/blob/2aabf3ce0569dd7c8c2d2a27944850056dcf2566/library/std/src/sys/sync/mutex/mod.rs#L3 * https://github.com/rust-lang/rust/blob/2aabf3ce0569dd7c8c2d2a27944850056dcf2566/library/std/src/sys/sync/mutex/futex.rs * https://github.com/rust-lang/rust/blob/2aabf3ce0569dd7c8c2d2a27944850056dcf2566/library/std/src/sys/sync/condvar/futex.rs This is a ~0.4% speedometer improvement on Windows (Linux and Android measurements in progress). This also adds a Linux implementation that will be enabled in a separate bug if worth it. Differential Revision: https://phabricator.services.mozilla.com/D300059
42 lines
1.5 KiB
C++
42 lines
1.5 KiB
C++
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "mozilla/PlatformConditionVariable.h"
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#include "mozilla/PlatformMutex.h"
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#include "mozilla/Futex.h"
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// All the memory orderings here are relaxed, because synchronization is done
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// by unlocking and locking the mutex.
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mozilla::detail::ConditionVariableImpl::ConditionVariableImpl() = default;
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mozilla::detail::ConditionVariableImpl::~ConditionVariableImpl() = default;
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void mozilla::detail::ConditionVariableImpl::notify_one() {
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mFutex.mValue.fetch_add(1, std::memory_order_relaxed);
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mFutex.wake();
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}
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void mozilla::detail::ConditionVariableImpl::notify_all() {
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mFutex.mValue.fetch_add(1, std::memory_order_relaxed);
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mFutex.wakeAll();
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}
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void mozilla::detail::ConditionVariableImpl::wait(MutexImpl& lock) {
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wait_for(lock, TimeDuration::Forever());
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}
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mozilla::CVStatus mozilla::detail::ConditionVariableImpl::wait_for(
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MutexImpl& lock, const mozilla::TimeDuration& rel_time) {
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// Examine the notification counter _before_ we unlock the mutex.
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uint32_t value = mFutex.mValue.load(std::memory_order_relaxed);
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// Unlock the mutex before going to sleep.
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lock.unlock();
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// Wait, but only if there hasn't been any notification since we unlocked the
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// mutex.
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bool r = mFutex.wait(value, &rel_time);
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// Lock the mutex again.
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lock.lock();
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return r ? CVStatus::NoTimeout : CVStatus::Timeout;
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}
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