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sx: unbreak debug after r326107

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An assertion was modified to use the found value, but it was not updated to
handle a race where blocked threads appear after the entrance to the func.

Move the assertion down to the area protected with sleepq lock where the
lock is read anyway. This does not affect coverage of the assertion and
is consistent with what rw locks are doing.

Reported by:	Shawn Webb
This commit is contained in:
Mateusz Guzik 2017-11-23 03:40:51 +00:00
parent 62b0676cde
commit 2d96bd8812
1 changed files with 1 additions and 1 deletions
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2
sys/kern/kern_sx.c
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@ -828,12 +828,12 @@ _sx_xunlock_hard(struct sx *sx, uintptr_t x LOCK_FILE_LINE_ARG_DEF)
atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
return;
MPASS(x & (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS));
if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR2(KTR_LOCK, "%s: %p contested", __func__, sx);
sleepq_lock(&sx->lock_object);
x = SX_READ_VALUE(sx);
MPASS(x & (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS));
/*
* The wake up algorithm here is quite simple and probably not