From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754058AbcAMQ1n (ORCPT ); Wed, 13 Jan 2016 11:27:43 -0500 Received: from e36.co.us.ibm.com ([32.97.110.154]:36989 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753715AbcAMQ1l (ORCPT ); Wed, 13 Jan 2016 11:27:41 -0500 X-IBM-Helo: d03dlp02.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Wed, 13 Jan 2016 08:27:33 -0800 From: "Paul E. McKenney" To: Kefeng Wang Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, guohanjun@huawei.com Subject: Re: [PATCH] locktorture: Fix NULL pointer when torture_type is invalid Message-ID: <20160113162733.GO3818@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1452650782-15099-1-git-send-email-wangkefeng.wang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1452650782-15099-1-git-send-email-wangkefeng.wang@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16011316-0021-0000-0000-0000160FCD98 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 13, 2016 at 10:06:22AM +0800, Kefeng Wang wrote: > Insmod locktorture with torture_type=mutex will lead to crash, > > Unable to handle kernel NULL pointer dereference at virtual address 00000008 > pgd = ffffffc0f6c10000 > [00000008] *pgd=000000013b221003, *pud=000000013b221003, *pmd=0000000000000000 > Internal error: Oops: 94000006 [#1] PREEMPT SMP > Modules linked in: locktorture(+) torture > CPU: 2 PID: 1462 Comm: insmod Not tainted 4.4.0+ #19 > Hardware name: linux,dummy-virt (DT) > task: ffffffc0fb2b3700 ti: ffffffc0fa938000 task.ti: ffffffc0fa938000 > PC is at __torture_print_stats+0x18/0x180 [locktorture] > LR is at lock_torture_stats_print+0x68/0x110 [locktorture] > pc : [] lr : [] pstate: 60000145 > sp : ffffffc0fa93bb20 > [snip...] > Call trace: > [] __torture_print_stats+0x18/0x180 [locktorture] > [] lock_torture_stats_print+0x68/0x110 [locktorture] > [] lock_torture_cleanup+0xc4/0x278 [locktorture] > [] lock_torture_init+0x144/0x5b0 [locktorture] > [] do_one_initcall+0x94/0x1a0 > [] do_init_module+0x60/0x1c8 > [] load_module+0x1880/0x1c9c > [] SyS_finit_module+0x7c/0x88 > [] el0_svc_naked+0x24/0x28 > > Fix it by check stats_task in lock_torture_cleanup() to guard not into > a wrong path. > > Signed-off-by: Kefeng Wang Good catch! One question below... > --- > kernel/locking/locktorture.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c > index 8ef1919..1afa8ad 100644 > --- a/kernel/locking/locktorture.c > +++ b/kernel/locking/locktorture.c > @@ -764,8 +764,10 @@ static void lock_torture_cleanup(void) > reader_tasks = NULL; > } > > - torture_stop_kthread(lock_torture_stats, stats_task); > - lock_torture_stats_print(); /* -After- the stats thread is stopped! */ > + if (stats_task) { > + torture_stop_kthread(lock_torture_stats, stats_task); > + lock_torture_stats_print(); /* -After- the stats thread is stopped! */ > + } Does it work to have the following? + if (stats_task) + torture_stop_kthread(lock_torture_stats, stats_task); + lock_torture_stats_print(); /* -After- the stats thread is stopped! */ We need to print the statistics at the end of the run, even if we chose not to print them periodically throughout the run. Thanx, Paul > if (atomic_read(&cxt.n_lock_torture_errors)) > lock_torture_print_module_parms(cxt.cur_ops, > -- > 1.7.12.4 >