From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: task imap:2958 blocked for more than 120 seconds Date: Wed, 13 Jan 2010 20:07:09 -0500 Message-ID: <20100114010709.GD3428@think> References: <201001102105.47192.johannes.hirte@fem.tu-ilmenau.de> <20100110201926.GC32195@think> <201001132337.34909.johannes.hirte@fem.tu-ilmenau.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org To: Johannes Hirte Return-path: In-Reply-To: <201001132337.34909.johannes.hirte@fem.tu-ilmenau.de> List-ID: On Wed, Jan 13, 2010 at 11:37:33PM +0100, Johannes Hirte wrote: > Am Sonntag 10 Januar 2010 21:19:26 schrieb Chris Mason: > > On Sun, Jan 10, 2010 at 09:05:46PM +0100, Johannes Hirte wrote: > > > I've observed this hanging task now several times. Not sure when this > > > started, but 2.6.32 is affected too, IIRC. I don't have a test pattern > > > for this. Dovecot imap triggers this from time to time. I've enabled > > > CONFIG_DETECT_HUNG_TASK now > > > > > and got this two tasks which hang: > > You're stuck on a read, could you please do a sysrq-w when this happens? > > Will do so when it happens again. No need, I reread the trace, you're stuck in copy_from_user and probably hitting a deadlock in the btrfs page faulting path. This is pretty rare, but I'll put it into the queue to fix up. > > > Also, do you eventually recover or are you stuck forever? > > I didn't wait too long when it happened, so I'm not sure. The longest time > I've waited was 20-30min, until reboot without recover. So either it's stuck > forever or it takes really long to recover. > > And one question I have: How do you identify a read in this call trace? Lock page followed by sync page is usually for reading. -chris