Commit-ID: cba77f03f2c7b6cc0b0a44a3c679e0abade7da62 Gitweb: http://git.kernel.org/tip/cba77f03f2c7b6cc0b0a44a3c679e0abade7da62 Author: Waiman Long <waiman.l...@hp.com> AuthorDate: Sat, 11 Jul 2015 21:19:19 -0400 Committer: Ingo Molnar <mi...@kernel.org> 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...@hitachi.com> Signed-off-by: Waiman Long <waiman.l...@hp.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/1436663959-53092-1-git-send-email-waiman.l...@hp.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
