From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH] ioprio: rcu_read_lock/unlock protect find_task_by_vpid call (V2) Date: Tue, 9 Nov 2010 21:20:50 +0100 Message-ID: <4CD9AD22.9030006@fusionio.com> References: <20101109102124.GA3916@swordfish.minsk.epam.com> <20101109201557.GS4032@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Sergey Senozhatsky , Alexander Viro , Andrew Morton , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Ingo Molnar , Tetsuo Handa To: "paulmck@linux.vnet.ibm.com" Return-path: In-Reply-To: <20101109201557.GS4032@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 2010-11-09 21:15, Paul E. McKenney wrote: > On Tue, Nov 09, 2010 at 12:21:24PM +0200, Sergey Senozhatsky wrote: >> Commit 4221a9918e38b7494cee341dda7b7b4bb8c04bde "Add RCU check for >> find_task_by_vpid()" introduced rcu_lockdep_assert to find_task_by_pid_ns.. >> Assertion failed in sys_ioprio_get. The patch is fixing assertion >> failure in ioprio_set as well. >> >> kernel/pid.c:419 invoked rcu_dereference_check() without protection! >> >> stack backtrace: >> Pid: 4254, comm: iotop Not tainted >> Call Trace: >> [] lockdep_rcu_dereference+0xaa/0xb2 >> [] find_task_by_pid_ns+0x4f/0x68 >> [] find_task_by_vpid+0x1d/0x1f >> [] sys_ioprio_get+0x50/0x2da >> [] system_call_fastpath+0x16/0x1b >> >> V2: rcu critical section expanded according to comment by Paul E. McKenne: >> | Looking over the patch again, the scope of the RCU read-side critical >> | section needs to expand to cover the use of the pointer as well as the >> | call to find_task_by_vpid(). > > Thank you, Sergey! > > Acked-by: Paul E. McKenney > > Jens, are you willing to take this one? Certainly, thanks guys! -- Jens Axboe