Re: Deadlocks due to per-process plugging

From: Thomas Gleixner
Date: Mon Jul 16 2012 - 04:59:56 EST

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?


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at