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authorWaiman Long <Waiman.Long@hp.com>2015-07-11 21:19:19 -0400
committerIngo Molnar <mingo@kernel.org>2015-07-21 10:18:07 +0200
commitcba77f03f2c7b6cc0b0a44a3c679e0abade7da62 (patch)
treedaba72ef7775e93627688ce9dd086a6e421c1feb /kernel/locking
parent9d634c410b07be7bf637ea03362d3ff132088fe3 (diff)
downloadlinux-cba77f03f2c7b6cc0b0a44a3c679e0abade7da62.tar.bz2
locking/pvqspinlock: Fix kernel panic in locking-selftest
Enabling locking-selftest in a VM guest may cause the following kernel panic: kernel BUG at .../kernel/locking/qspinlock_paravirt.h:137! This is due to the fact that the pvqspinlock unlock function is expecting either a _Q_LOCKED_VAL or _Q_SLOW_VAL in the lock byte. This patch prevents that bug report by ignoring it when debug_locks_silent is set. Otherwise, a warning will be printed if it contains an unexpected value. With this patch applied, the kernel locking-selftest completed without any noise. Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Waiman Long <Waiman.Long@hp.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1436663959-53092-1-git-send-email-Waiman.Long@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking')
-rw-r--r--kernel/locking/qspinlock_paravirt.h11
1 files changed, 10 insertions, 1 deletions
diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index 04ab18151cc8..df19ae4debd0 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -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.