Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934835AbaFTQW4 (ORCPT ); Fri, 20 Jun 2014 12:22:56 -0400 Received: from g2t2354.austin.hp.com ([15.217.128.53]:57718 "EHLO g2t2354.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934758AbaFTQWz (ORCPT ); Fri, 20 Jun 2014 12:22:55 -0400 From: Waiman Long To: Ingo Molnar , Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Scott J Norton , Waiman Long Subject: [PATCH] lockdep: restrict the use of recursive read_lock with qrwlock Date: Fri, 20 Jun 2014 12:22:43 -0400 Message-Id: <1403281363-33403-1-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 Unlike the original unfair rwlock implementation, queued rwlock will grant lock according to the chronological sequence of the lock requests except when the lock requester is in the interrupt context. As a result, recursive read_lock calls will hang the process if there is a write_lock call somewhere in between the read_lock calls. This patch updates the lockdep implementation to look for recursive read_lock calls when queued rwlock is being used. Signed-off-by: Waiman Long --- kernel/locking/lockdep.c | 12 ++++++++++++ 1 files changed, 12 insertions(+), 0 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index d24e433..b6c9f2e 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1766,12 +1766,22 @@ check_deadlock(struct task_struct *curr, struct held_lock *next, if (hlock_class(prev) != hlock_class(next)) continue; +#ifdef CONFIG_QUEUE_RWLOCK + /* + * Queue rwlock only allows read-after-read recursion of the + * same lock class when the latter read is in an interrupt + * context. + */ + if ((read == 2) && prev->read && in_interrupt()) + return 2; +#else /* * Allow read-after-read recursion of the same * lock class (i.e. read_lock(lock)+read_lock(lock)): */ if ((read == 2) && prev->read) return 2; +#endif /* * We're holding the nest_lock, which serializes this lock's @@ -1852,8 +1862,10 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, * write-lock never takes any other locks, then the reads are * equivalent to a NOP. */ +#ifndef CONFIG_QUEUE_RWLOCK if (next->read == 2 || prev->read == 2) return 1; +#endif /* * Is the -> dependency already present? * -- 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/