Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752126AbbGLBTg (ORCPT ); Sat, 11 Jul 2015 21:19:36 -0400 Received: from g9t5008.houston.hp.com ([15.240.92.66]:34912 "EHLO g9t5008.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752012AbbGLBTf (ORCPT ); Sat, 11 Jul 2015 21:19:35 -0400 From: Waiman Long To: Peter Zijlstra , Ingo Molnar Cc: linux-kernel@vger.kernel.org, Masami Hiramatsu , Waiman Long Subject: [PATCH] locking/pvqspinlock: Fix kernel panic in locking-selftest Date: Sat, 11 Jul 2015 21:19:19 -0400 Message-Id: <1436663959-53092-1-git-send-email-Waiman.Long@hp.com> X-Mailer: git-send-email 1.7.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2189 Lines: 65 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. Signed-off-by: Waiman Long --- kernel/locking/qspinlock_paravirt.h | 12 +++++++++++- 1 files changed, 11 insertions(+), 1 deletions(-) diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h index 04ab181..15d3733 100644 --- a/kernel/locking/qspinlock_paravirt.h +++ b/kernel/locking/qspinlock_paravirt.h @@ -4,6 +4,7 @@ #include #include +#include /* * Implement paravirt qspinlocks; the general idea is to halt the vcpus instead @@ -286,15 +287,24 @@ __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 0x%lx has corrupted value 0x%x!\n", + (unsigned long)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. -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/