From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754359AbaFSMiE (ORCPT ); Thu, 19 Jun 2014 08:38:04 -0400 Received: from terminus.zytor.com ([198.137.202.10]:57552 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751413AbaFSMiA (ORCPT ); Thu, 19 Jun 2014 08:38:00 -0400 Date: Thu, 19 Jun 2014 05:36:52 -0700 From: tip-bot for Trond Myklebust Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org, trond.myklebust@primarydata.com, peterz@infradead.org, sboyd@codeaurora.org, viro@zeniv.linux.org.uk, davem@davemloft.net, john.stultz@linaro.org, Waiman.Long@hp.com, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, trond.myklebust@primarydata.com, torvalds@linux-foundation.org, peterz@infradead.org, viro@zeniv.linux.org.uk, sboyd@codeaurora.org, davem@davemloft.net, john.stultz@linaro.org, Waiman.Long@hp.com, tglx@linutronix.de In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/core] lockdep: Revert lockdep check in raw_seqcount_begin() Git-Commit-ID: 22fdcf02f6e80d64a927f702dd9d631a927d87d4 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 22fdcf02f6e80d64a927f702dd9d631a927d87d4 Gitweb: http://git.kernel.org/tip/22fdcf02f6e80d64a927f702dd9d631a927d87d4 Author: Trond Myklebust AuthorDate: Thu, 5 Jun 2014 11:31:01 -0400 Committer: Ingo Molnar CommitDate: Wed, 18 Jun 2014 18:41:23 +0200 lockdep: Revert lockdep check in raw_seqcount_begin() This commit reverts the addition of lockdep checking to raw_seqcount_begin for the following reasons: 1) It violates the naming convention that raw_* functions should not do lockdep checks (a convention that is also followed by the other raw_*_seqcount_begin functions). 2) raw_seqcount_begin does not spin, so it can only be part of an ABBA deadlock in very special circumstances (for instance if a lock is held across the entire raw_seqcount_begin()+read_seqcount_retry() loop while also being taken inside the write_seqcount protected area). 3) It is causing false positives with some existing callers, and there is no non-lockdep alternative for those callers to use. None of the three existing callers (__d_lookup_rcu, netdev_get_name, and the NFS state code) appear to use the function in a manner that is ABBA deadlock prone. Fixes: 1ca7d67cf5d5: seqcount: Add lockdep functionality to seqcount/seqlock Signed-off-by: Trond Myklebust Signed-off-by: Peter Zijlstra Cc: John Stultz Cc: "David S. Miller" Cc: Al Viro Cc: Waiman Long Cc: Stephen Boyd Cc: Linus Torvalds Link: http://lkml.kernel.org/r/CAHQdGtRR6SvEhXiqWo24hoUh9AU9cL82Z8Z-d8-7u951F_d+5g@mail.gmail.com Signed-off-by: Ingo Molnar --- include/linux/seqlock.h | 2 -- 1 file changed, 2 deletions(-) diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index 535f158..8cf3503 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -164,8 +164,6 @@ static inline unsigned read_seqcount_begin(const seqcount_t *s) static inline unsigned raw_seqcount_begin(const seqcount_t *s) { unsigned ret = ACCESS_ONCE(s->sequence); - - seqcount_lockdep_reader_access(s); smp_rmb(); return ret & ~1; }