Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933844Ab3HHCeF (ORCPT ); Wed, 7 Aug 2013 22:34:05 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:52159 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933769Ab3HHCeC (ORCPT ); Wed, 7 Aug 2013 22:34:02 -0400 Date: Wed, 7 Aug 2013 19:33:56 -0700 From: "Paul E. McKenney" To: Lai Jiangshan Cc: Steven Rostedt , Peter Zijlstra , linux-kernel@vger.kernel.org, C.Emde@osadl.org Subject: Re: [PATCH 0/8] rcu: Ensure rcu read site is deadlock-immunity Message-ID: <20130808023356.GG4306@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1375871104-10688-1-git-send-email-laijs@cn.fujitsu.com> <20130807123827.GB4306@linux.vnet.ibm.com> <20130808003635.GA9487@linux.vnet.ibm.com> <5202F8CC.2020703@cn.fujitsu.com> <1375927932.6848.33.camel@gandalf.local.home> <5203036B.2080606@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5203036B.2080606@cn.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13080802-7606-0000-0000-00000E1CFA7A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4611 Lines: 92 On Thu, Aug 08, 2013 at 10:33:15AM +0800, Lai Jiangshan wrote: > On 08/08/2013 10:12 AM, Steven Rostedt wrote: > > On Thu, 2013-08-08 at 09:47 +0800, Lai Jiangshan wrote: > > > >>> [ 393.641012] CPU0 > >>> [ 393.641012] ---- > >>> [ 393.641012] lock(&lock->wait_lock); > >>> [ 393.641012] > >>> [ 393.641012] lock(&lock->wait_lock); > >> > >> Patch2 causes it! > >> When I found all lock which can (chained) nested in rcu_read_unlock_special(), > >> I didn't notice rtmutex's lock->wait_lock is not nested in irq-disabled. > >> > >> Two ways to fix it: > >> 1) change rtmutex's lock->wait_lock, make it alwasys irq-disabled. > >> 2) revert my patch2 > > > > Your patch 2 states: > > > > "After patch 10f39bb1, "special & RCU_READ_UNLOCK_BLOCKED" can't be true > > in irq nor softirq.(due to RCU_READ_UNLOCK_BLOCKED can only be set > > when preemption)" > > Patch5 adds "special & RCU_READ_UNLOCK_BLOCKED" back in irq nor softirq. > This new thing is handle in patch5 if I did not do wrong things in patch5. > (I don't notice rtmutex's lock->wait_lock is not irqs-disabled in patch5) > > > > > But then below we have: > > > > > >> > >>> [ 393.641012] > >>> [ 393.641012] *** DEADLOCK *** > >>> [ 393.641012] > >>> [ 393.641012] no locks held by rcu_torture_rea/697. > >>> [ 393.641012] > >>> [ 393.641012] stack backtrace: > >>> [ 393.641012] CPU: 3 PID: 697 Comm: rcu_torture_rea Not tainted 3.11.0-rc1+ #1 > >>> [ 393.641012] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007 > >>> [ 393.641012] ffffffff8586fea0 ffff88001fcc3a78 ffffffff8187b4cb ffffffff8104a261 > >>> [ 393.641012] ffff88001e1a20c0 ffff88001fcc3ad8 ffffffff818773e4 0000000000000000 > >>> [ 393.641012] ffff880000000000 ffff880000000001 ffffffff81010a0a 0000000000000001 > >>> [ 393.641012] Call Trace: > >>> [ 393.641012] [] dump_stack+0x4f/0x84 > >>> [ 393.641012] [] ? console_unlock+0x291/0x410 > >>> [ 393.641012] [] print_usage_bug+0x1f5/0x206 > >>> [ 393.641012] [] ? save_stack_trace+0x2a/0x50 > >>> [ 393.641012] [] mark_lock+0x283/0x2e0 > >>> [ 393.641012] [] ? print_irq_inversion_bug.part.40+0x1f0/0x1f0 > >>> [ 393.641012] [] __lock_acquire+0x906/0x1d40 > >>> [ 393.641012] [] ? __lock_acquire+0x2eb/0x1d40 > >>> [ 393.641012] [] ? __lock_acquire+0x2eb/0x1d40 > >>> [ 393.641012] [] lock_acquire+0x95/0x210 > >>> [ 393.641012] [] ? rt_mutex_unlock+0x53/0x100 > >>> [ 393.641012] [] _raw_spin_lock+0x36/0x50 > >>> [ 393.641012] [] ? rt_mutex_unlock+0x53/0x100 > >>> [ 393.641012] [] rt_mutex_unlock+0x53/0x100 > >>> [ 393.641012] [] rcu_read_unlock_special+0x17a/0x2a0 > >>> [ 393.641012] [] rcu_check_callbacks+0x313/0x950 > >>> [ 393.641012] [] ? hrtimer_run_queues+0x1d/0x180 > >>> [ 393.641012] [] ? trace_hardirqs_off+0xd/0x10 > >>> [ 393.641012] [] update_process_times+0x43/0x80 > >>> [ 393.641012] [] tick_sched_handle.isra.10+0x31/0x40 > >>> [ 393.641012] [] tick_sched_timer+0x47/0x70 > >>> [ 393.641012] [] __run_hrtimer+0x7c/0x490 > >>> [ 393.641012] [] ? ktime_get_update_offsets+0x4d/0xe0 > >>> [ 393.641012] [] ? tick_nohz_handler+0xa0/0xa0 > >>> [ 393.641012] [] hrtimer_interrupt+0x107/0x260 > > > > The hrtimer_interrupt is calling a rt_mutex_unlock? How did that happen? > > Did it first call a rt_mutex_lock? > > > > If patch two was the culprit, I'm thinking the idea behind patch two is > > wrong. The only option is to remove patch number two! > > removing patch number two can solve the problem found be Paul, but it is not the best. > because I can't declare that rcu is deadlock-immunity > (it will be deadlock if rcu read site overlaps with rtmutex's lock->wait_lock > if I only remove patch2) > I must do more things, but I think it is still better than changing rtmutex's lock->wait_lock. NP, I will remove your current patches and wait for an updated set. Thanx, Paul -- 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/