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Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull locking fix from Ingo Molnar:
 "A single fix for a locking self-test crash"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/pvqspinlock: Fix kernel panic in locking-selftest
This commit is contained in:
Linus Torvalds 2015-08-14 10:45:23 -07:00
parent c679765416 cba77f03f2
commit 5e5013c6b5
1 changed files with 10 additions and 1 deletions
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11
kernel/locking/qspinlock_paravirt.h
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@ -4,6 +4,7 @@
#include <linux/hash.h>
#include <linux/bootmem.h>
#include <linux/debug_locks.h>
/*
* Implement paravirt qspinlocks; the general idea is to halt the vcpus instead
@ -286,15 +287,23 @@ __visible void __pv_queued_spin_unlock(struct qspinlock *lock)
{
struct __qspinlock *l = (void *)lock;
struct pv_node *node;
u8 lockval = cmpxchg(&l->locked, _Q_LOCKED_VAL, 0);
/*
* We must not unlock if SLOW, because in that case we must first
* unhash. Otherwise it would be possible to have multiple @lock
* entries, which would be BAD.
*/
if (likely(cmpxchg(&l->locked, _Q_LOCKED_VAL, 0) == _Q_LOCKED_VAL))
if (likely(lockval == _Q_LOCKED_VAL))
return;
if (unlikely(lockval != _Q_SLOW_VAL)) {
if (debug_locks_silent)
return;
WARN(1, "pvqspinlock: lock %p has corrupted value 0x%x!\n", lock, atomic_read(&lock->val));
return;
}
/*
* Since the above failed to release, this must be the SLOW path.
* Therefore start by looking up the blocked node and unhashing it.