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Kernel: Fix blocking relock of the big_lock while unlocking other Lock

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When a Thread is being unblocked and we need to re-lock the process
big_lock and re-locking blocks again, then we may end up in
Thread::block again while still servicing the original lock's
Thread::block. So permit recursion as long as it's only the big_lock
that we block on again.

Fixes #8822
This commit is contained in:
Tom 2021-07-16 15:48:22 -06:00 • committed by Andreas Kling
parent 06ddfcde89
commit ae8472f9ca
1 changed files with 9 additions and 6 deletions
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15
Kernel/Thread.cpp
View file

@ -180,8 +180,6 @@ void Thread::block(Kernel::Mutex& lock, ScopedSpinLock<SpinLock<u8>>& lock_lock,
VERIFY(!s_mm_lock.own_lock());
ScopedSpinLock block_lock(m_block_lock);
VERIFY(!m_in_block);
m_in_block = true;
ScopedSpinLock scheduler_lock(g_scheduler_lock);
@ -195,7 +193,14 @@ void Thread::block(Kernel::Mutex& lock, ScopedSpinLock<SpinLock<u8>>& lock_lock,
default:
VERIFY_NOT_REACHED();
}
VERIFY(!m_blocking_lock);
// If we're blocking on the big-lock we may actually be in the process
// of unblocking from another lock. If that's the case m_blocking_lock
// is already set
auto& big_lock = process().big_lock();
VERIFY((&lock == &big_lock && m_blocking_lock != &big_lock) || !m_blocking_lock);
auto previous_blocking_lock = m_blocking_lock;
m_blocking_lock = &lock;
m_lock_requested_count = lock_count;
@ -208,7 +213,6 @@ void Thread::block(Kernel::Mutex& lock, ScopedSpinLock<SpinLock<u8>>& lock_lock,
dbgln_if(THREAD_DEBUG, "Thread {} blocking on Mutex {}", *this, &lock);
auto& big_lock = process().big_lock();
for (;;) {
// Yield to the scheduler, and wait for us to resume unblocked.
VERIFY(!g_scheduler_lock.own_lock());
@ -230,8 +234,7 @@ void Thread::block(Kernel::Mutex& lock, ScopedSpinLock<SpinLock<u8>>& lock_lock,
}
VERIFY(!m_blocking_lock);
VERIFY(m_in_block);
m_in_block = false;
m_blocking_lock = previous_blocking_lock;
break;
}