From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: Deadlocks due to per-process plugging Date: Mon, 16 Jul 2012 10:59:46 +0200 (CEST) Message-ID: References: <20120711133735.GA8122@quack.suse.cz> <20120711201601.GB9779@quack.suse.cz> <20120713123318.GB20361@quack.suse.cz> <20120713144622.GB28715@quack.suse.cz> <1342343673.28142.2.camel@marge.simpson.net> <1342405366.7659.35.camel@marge.simpson.net> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Jan Kara , Jeff Moyer , LKML , linux-fsdevel@vger.kernel.org, Tejun Heo , Jens Axboe , mgalbraith@suse.com To: Mike Galbraith Return-path: In-Reply-To: <1342405366.7659.35.camel@marge.simpson.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Mon, 16 Jul 2012, Mike Galbraith wrote: > On Sun, 2012-07-15 at 11:14 +0200, Mike Galbraith wrote: > > On Sun, 2012-07-15 at 10:59 +0200, Thomas Gleixner wrote: > > > > Can you figure out on which lock the stuck thread which did not unplug > > > due to tsk_is_pi_blocked was blocked? > > > > I'll take a peek. > > Sorry for late reply, took a half day away from box. Jan had already > done the full ext3 IO deadlock analysis: > > Again kjournald is waiting for buffer IO on block 4367635 (sector > 78364838) to finish. Now it is dbench thread 0xffff88026f330e70 which > has submitted this buffer for IO and is still holding this buffer behind > its plug (request for sector 78364822..78364846). The dbench thread is > waiting on j_checkpoint mutex (apparently it has successfully got the > mutex in the past, checkpointed some buffers, released the mutex and > hung when trying to acquire it again in the next loop of > __log_wait_for_space()). And what's holding j_checkpoint mutex and not making progress? Thanks, tglx