From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933033AbcEKN7q (ORCPT ); Wed, 11 May 2016 09:59:46 -0400 Received: from mx2.suse.de ([195.135.220.15]:60504 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932753AbcEKN7o (ORCPT ); Wed, 11 May 2016 09:59:44 -0400 Date: Wed, 11 May 2016 15:59:39 +0200 From: Michal Hocko To: Peter Zijlstra Cc: Tetsuo Handa , LKML , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , "David S. Miller" , Tony Luck , Andrew Morton , Chris Zankel , Max Filippov , Davidlohr Bueso , Waiman Long Subject: Re: [PATCH 03/11] locking, rwsem: introduce basis for down_write_killable Message-ID: <20160511135938.GA19577@dhcp22.suse.cz> References: <8bd03bdc-0373-a3bb-da12-045322efb797@I-love.SAKURA.ne.jp> <20160510115320.GJ23576@dhcp22.suse.cz> <20160510123806.GB3193@twins.programming.kicks-ass.net> <20160511072357.GC16677@dhcp22.suse.cz> <20160511082853.GF16677@dhcp22.suse.cz> <20160511084401.GH3193@twins.programming.kicks-ass.net> <20160511090442.GH16677@dhcp22.suse.cz> <20160511091733.GC3192@twins.programming.kicks-ass.net> <20160511093127.GI16677@dhcp22.suse.cz> <20160511094128.GB3190@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160511094128.GB3190@twins.programming.kicks-ass.net> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 11-05-16 11:41:28, Peter Zijlstra wrote: > On Wed, May 11, 2016 at 11:31:27AM +0200, Michal Hocko wrote: > > > Care to cook up a full patch? > > compile tested only, if someone could please test it? I have tried to run the test case from Tetsuo[1] with a small printk to show the interrupted writer case: [ 2753.596678] XXX: Writer interrupted. Woken waiters:0 [ 2998.266978] XXX: Writer interrupted. Woken waiters:0 which means rwsem_atomic_update(-RWSEM_WAITING_BIAS, sem) path which is the problematic case. oom_reaper was always able to succeed so I guess the patch works as expected. I will leave the test run for longer to be sure. [1] http://lkml.kernel.org/r/201605061958.HHG48967.JVFtSLFQOFOOMH@I-love.SAKURA.ne.jp > > I'll go write a Changelog if it turns out to actually work ;-) > > --- > kernel/locking/rwsem-xadd.c | 21 +++++++++++++++------ > 1 file changed, 15 insertions(+), 6 deletions(-) > > diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c > index df4dcb883b50..09e30c6225e5 100644 > --- a/kernel/locking/rwsem-xadd.c > +++ b/kernel/locking/rwsem-xadd.c > @@ -487,23 +487,32 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state) > > /* Block until there are no active lockers. */ > do { > - if (signal_pending_state(state, current)) { > - raw_spin_lock_irq(&sem->wait_lock); > - ret = ERR_PTR(-EINTR); > - goto out; > - } > + if (signal_pending_state(state, current)) > + goto out_nolock; > + > schedule(); > set_current_state(state); > } while ((count = sem->count) & RWSEM_ACTIVE_MASK); > > raw_spin_lock_irq(&sem->wait_lock); > } > -out: > __set_current_state(TASK_RUNNING); > list_del(&waiter.list); > raw_spin_unlock_irq(&sem->wait_lock); > > return ret; > + > +out_nolock: > + __set_current_state(TASK_RUNNING); > + raw_spin_lock_irq(&sem->wait_lock); > + list_del(&waiter.list); > + if (list_empty(&sem->wait_list)) > + rwsem_atomic_update(-RWSEM_WAITING_BIAS, sem); > + else > + __rwsem_do_wake(sem, RWSEM_WAKE_ANY); > + raw_spin_unlock_irq(&sem->wait_lock); > + > + return ERR_PTR(-EINTR); > } > > __visible struct rw_semaphore * __sched -- Michal Hocko SUSE Labs