From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20120205220950.684814014@pcw.home.local> Date: Sun, 05 Feb 2012 23:10:18 +0100 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Shaohua Li , Jens Axboe , Greg KH Subject: [PATCH 29/91] cfq-iosched: fix a rcu warning In-Reply-To: <0635750f5f06ed2ca212b91fcb5c4483@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: 2.6.27-longterm review patch. If anyone has any objections, please let us know. ------------------ commit 3181faa85bda3dc3f5e630a1846526c9caaa38e3 upstream. I got a rcu warnning at boot. the ioc->ioc_data is rcu_deferenced, but doesn't hold rcu_read_lock. Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/cfq-iosched.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) Index: longterm-2.6.27/block/cfq-iosched.c =================================================================== --- longterm-2.6.27.orig/block/cfq-iosched.c 2012-02-05 22:34:38.850917663 +0100 +++ longterm-2.6.27/block/cfq-iosched.c 2012-02-05 22:34:38.987917155 +0100 @@ -1286,11 +1286,14 @@ cic->dead_key = (unsigned long) cic->key; cic->key = NULL; + rcu_read_lock(); if (rcu_dereference(ioc->ioc_data) == cic) { + rcu_read_unlock(); spin_lock(&ioc->lock); rcu_assign_pointer(ioc->ioc_data, NULL); spin_unlock(&ioc->lock); - } + } else + rcu_read_unlock(); if (cic->cfqq[ASYNC]) { cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);