Commit-ID: cba77f03f2c7b6cc0b0a44a3c679e0abade7da62
Gitweb: http://git.kernel.org/tip/cba77f03f2c7b6cc0b0a44a3c679e0abade7da62
Author: Waiman Long <Waiman.Long@xxxxxx>
AuthorDate: Sat, 11 Jul 2015 21:19:19 -0400
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 21 Jul 2015 10:18:07 +0200
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@xxxxxxxxxxx>
Signed-off-by: Waiman Long <Waiman.Long@xxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1436663959-53092-1-git-send-email-Waiman.Long@xxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/locking/qspinlock_paravirt.h | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index 04ab181..df19ae4 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.
--
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