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path: root/Kernel/WaitQueue.cpp
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2020-01-18Meta: Add license header to source filesAndreas Kling
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.
2020-01-12Kernel: Fix Lock racing to the WaitQueueAndreas Kling
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().
2019-12-22Kernel: Use IntrusiveList to make WaitQueue allocation-free :^)Andreas Kling
2019-12-08Kernel: Break out of the idle loop on WaitQueue wake instead of on IRQAndreas Kling
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.
2019-12-01Kernel: Use a dedicated thread state for wait-queued threadsAndreas Kling
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.
2019-12-01Kernel: Add a WaitQueue for Thread queueing/waking and use it for LockAndreas Kling
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.