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Kernel: Fix Lock racing to the WaitQueue

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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().
This commit is contained in:
Andreas Kling 2020-01-12 18:46:41 +01:00
parent 61e6b1fb7c
commit 41376d4662
5 changed files with 13 additions and 10 deletions
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9
Kernel/Lock.cpp
View file

@ -18,8 +18,7 @@ void Lock::lock()
m_lock.store(false, AK::memory_order_release);
return;
}
m_lock.store(false, AK::memory_order_release);
current->wait_on(m_queue, m_holder, m_name);
current->wait_on(m_queue, &m_lock, m_holder, m_name);
}
}
}
@ -37,8 +36,7 @@ void Lock::unlock()
return;
}
m_holder = nullptr;
m_queue.wake_one();
m_lock.store(false, AK::memory_order_release);
m_queue.wake_one(&m_lock);
return;
}
// I don't know *who* is using "m_lock", so just yield.
@ -66,8 +64,7 @@ bool Lock::unlock_if_locked()
return false;
}
m_holder = nullptr;
m_lock.store(false, AK::memory_order_release);
m_queue.wake_one();
m_queue.wake_one(&m_lock);
return true;
}
// I don't know *who* is using "m_lock", so just yield.