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 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
