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ladybird/Kernel/WaitQueue.cpp

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Meta: Add license header to source files As suggested by Joshua, this commit adds the 2-clause BSD license as a comment block to the top of every source file. For the first pass, I've just added myself for simplicity. I encourage everyone to add themselves as copyright holders of any file they've added or modified in some significant way. If I've added myself in error somewhere, feel free to replace it with the appropriate copyright holder instead. Going forward, all new source files should include a license header.
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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT HOLDER OR 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.
*/
Kernel: Add a WaitQueue for Thread queueing/waking and use it for Lock The kernel's Lock class now uses a proper wait queue internally instead of just having everyone wake up regularly to try to acquire the lock. We also keep the donation mechanism, so that whenever someone tries to take the lock and fails, that thread donates the remainder of its timeslice to the current lock holder. After unlocking a Lock, the unlocking thread calls WaitQueue::wake_one, which unblocks the next thread in queue.
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#include <Kernel/Thread.h>
#include <Kernel/WaitQueue.h>
Kernel: Move all code into the Kernel namespace
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namespace Kernel {
Kernel: Add a WaitQueue for Thread queueing/waking and use it for Lock The kernel's Lock class now uses a proper wait queue internally instead of just having everyone wake up regularly to try to acquire the lock. We also keep the donation mechanism, so that whenever someone tries to take the lock and fails, that thread donates the remainder of its timeslice to the current lock holder. After unlocking a Lock, the unlocking thread calls WaitQueue::wake_one, which unblocks the next thread in queue.
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WaitQueue::WaitQueue()
{
}
WaitQueue::~WaitQueue()
{
}
void WaitQueue::enqueue(Thread& thread)
{
InterruptDisabler disabler;
Kernel: Use IntrusiveList to make WaitQueue allocation-free :^)
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m_threads.append(thread);
Kernel: Add a WaitQueue for Thread queueing/waking and use it for Lock The kernel's Lock class now uses a proper wait queue internally instead of just having everyone wake up regularly to try to acquire the lock. We also keep the donation mechanism, so that whenever someone tries to take the lock and fails, that thread donates the remainder of its timeslice to the current lock holder. After unlocking a Lock, the unlocking thread calls WaitQueue::wake_one, which unblocks the next thread in queue.
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}
Kernel: Fix Lock racing to the WaitQueue There was a time window between releasing Lock::m_lock and calling into the lock's WaitQueue where someone else could take m_lock and bring two threads into a deadlock situation. Fix this issue by holding Lock::m_lock until interrupts are disabled by either Thread::wait_on() or WaitQueue::wake_one().
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void WaitQueue::wake_one(Atomic<bool>* lock)
Kernel: Add a WaitQueue for Thread queueing/waking and use it for Lock The kernel's Lock class now uses a proper wait queue internally instead of just having everyone wake up regularly to try to acquire the lock. We also keep the donation mechanism, so that whenever someone tries to take the lock and fails, that thread donates the remainder of its timeslice to the current lock holder. After unlocking a Lock, the unlocking thread calls WaitQueue::wake_one, which unblocks the next thread in queue.
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{
InterruptDisabler disabler;
Kernel: Fix Lock racing to the WaitQueue There was a time window between releasing Lock::m_lock and calling into the lock's WaitQueue where someone else could take m_lock and bring two threads into a deadlock situation. Fix this issue by holding Lock::m_lock until interrupts are disabled by either Thread::wait_on() or WaitQueue::wake_one().
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if (lock)
*lock = false;
Kernel: Add a WaitQueue for Thread queueing/waking and use it for Lock The kernel's Lock class now uses a proper wait queue internally instead of just having everyone wake up regularly to try to acquire the lock. We also keep the donation mechanism, so that whenever someone tries to take the lock and fails, that thread donates the remainder of its timeslice to the current lock holder. After unlocking a Lock, the unlocking thread calls WaitQueue::wake_one, which unblocks the next thread in queue.
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if (m_threads.is_empty())
return;
if (auto* thread = m_threads.take_first())
Kernel: Use a dedicated thread state for wait-queued threads Instead of using the generic block mechanism, wait-queued threads now go into the special Queued state. This fixes an issue where signal dispatch would unblock a wait-queued thread (because signal dispatch unblocks blocked threads) and cause confusion since the thread only expected to be awoken by the queue.
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thread->wake_from_queue();
Kernel: Break out of the idle loop on WaitQueue wake instead of on IRQ Now that we have proper wait queues to drive waiter wakeup, we can use the wake actions to break out of the scheduler's idle loop when we've got a thread to run.
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Scheduler::stop_idling();
Kernel: Add a WaitQueue for Thread queueing/waking and use it for Lock The kernel's Lock class now uses a proper wait queue internally instead of just having everyone wake up regularly to try to acquire the lock. We also keep the donation mechanism, so that whenever someone tries to take the lock and fails, that thread donates the remainder of its timeslice to the current lock holder. After unlocking a Lock, the unlocking thread calls WaitQueue::wake_one, which unblocks the next thread in queue.
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}
void WaitQueue::wake_all()
{
InterruptDisabler disabler;
if (m_threads.is_empty())
return;
while (!m_threads.is_empty())
Kernel: Use a dedicated thread state for wait-queued threads Instead of using the generic block mechanism, wait-queued threads now go into the special Queued state. This fixes an issue where signal dispatch would unblock a wait-queued thread (because signal dispatch unblocks blocked threads) and cause confusion since the thread only expected to be awoken by the queue.
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m_threads.take_first()->wake_from_queue();
Kernel: Break out of the idle loop on WaitQueue wake instead of on IRQ Now that we have proper wait queues to drive waiter wakeup, we can use the wake actions to break out of the scheduler's idle loop when we've got a thread to run.
2019-12-07 23:33:35 +00:00
Scheduler::stop_idling();
Kernel: Add a WaitQueue for Thread queueing/waking and use it for Lock The kernel's Lock class now uses a proper wait queue internally instead of just having everyone wake up regularly to try to acquire the lock. We also keep the donation mechanism, so that whenever someone tries to take the lock and fails, that thread donates the remainder of its timeslice to the current lock holder. After unlocking a Lock, the unlocking thread calls WaitQueue::wake_one, which unblocks the next thread in queue.
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}
Kernel: Move all code into the Kernel namespace
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Kernel: Allow process with multiple threads to call exec and exit This allows a process wich has more than 1 thread to call exec, even from a thread. This kills all the other threads, but it won't wait for them to finish, just makes sure that they are not in a running/runable state. In the case where a thread does exec, the new program PID will be the thread TID, to keep the PID == TID in the new process. This introduces a new function inside the Process class, kill_threads_except_self which is called on exit() too (exit with multiple threads wasn't properly working either). Inside the Lock class, there is the need for a new function, clear_waiters, which removes all the waiters from the Process::big_lock. This is needed since after a exit/exec, there should be no other threads waiting for this lock, the threads should be simply killed. Only queued threads should wait for this lock at this point, since blocked threads are handled in set_should_die.
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void WaitQueue::clear()
{
InterruptDisabler disabler;
m_threads.clear();
}
Kernel: Move all code into the Kernel namespace
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}
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