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authorRich Felker <dalias@aerifal.cx>2020-10-30 11:21:06 -0400
committerRich Felker <dalias@aerifal.cx>2020-10-30 11:21:06 -0400
commit27b2fc9d6db956359727a66c262f1e69995660aa (patch)
tree457269a4769dbf8873bd3479fbbbeb5b9f03539f /arch/aarch64
parent7c71792e87691451f2a6b76348e83ad1889f1dcb (diff)
downloadmusl-27b2fc9d6db956359727a66c262f1e69995660aa.tar.gz
fix missing-wake regression in pthread_cond_wait
the reasoning in commit 2d0bbe6c788938d1332609c014eeebc1dff966ac was not entirely correct. while it's true that setting the waiters flag ensures that the next unlock will perform a wake, it's possible that the wake is consumed by a mutex waiter that has no relationship with the condvar wait queue being processed, which then takes the mutex. when that thread subsequently unlocks, it sees no waiters, and leaves the rest of the condvar queue stuck. bring back the waiter count adjustment, but skip it for PI mutexes, for which a successful lock-after-waiting always sets the waiters bit. if future changes are made to bring this same waiters-bit contract to all lock types, this can be reverted.
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