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There is a window between acquiring/releasing the lock with the atomic variables and subsequently waiting or waking threads. With a single processor this window was closed by using a critical section, but this doesn't prevent other processors from running these code paths. To solve this, set a flag in the WaitQueue while holding m_lock which determines if threads should be blocked at all.
61 lines
2.1 KiB
C++
61 lines
2.1 KiB
C++
/*
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* Copyright (c) 2020, The SerenityOS developers.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Atomic.h>
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#include <Kernel/SpinLock.h>
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#include <Kernel/Thread.h>
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namespace Kernel {
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class WaitQueue : public Thread::BlockCondition {
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public:
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u32 wake_one();
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u32 wake_n(u32 wake_count);
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u32 wake_all();
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void should_block(bool block)
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{
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ScopedSpinLock lock(m_lock);
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m_should_block = block;
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}
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template<class... Args>
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Thread::BlockResult wait_on(const Thread::BlockTimeout& timeout, Args&&... args)
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{
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return Thread::current()->block<Thread::QueueBlocker>(timeout, *this, forward<Args>(args)...);
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}
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protected:
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virtual bool should_add_blocker(Thread::Blocker& b, void* data) override;
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private:
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bool m_wake_requested { false };
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bool m_should_block { true };
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};
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}
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