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Date: Mon, 16 Jul 2012 13:03:15 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: Mike Galbraith <efault@....de> Cc: Chris Mason <chris.mason@...ionio.com>, "Chris L. Mason" <clmason@...ionio.com>, "linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: 3.4.4-rt13: btrfs + xfstests 006 = BOOM.. and a bonus rt_mutex deadlock report for absolutely free! On Mon, 2012-07-16 at 18:36 +0200, Mike Galbraith wrote: > > > > Ouch, you just turned the rt_read_lock() into a spin lock. If a higher > > > priority process preempted a lower priority process that holds the same > > > lock, it will deadlock. > > > > Hm, how, it's doing cpu_chill()? > > 'course PI is toast, so *poof*. Since just enabling the lockdep bits > seems to fix it up, maybe that's the patchlet to submit (less is more). There's that too. But the issue I was talking about is with all trylock loops. As holding an rt-mutex now disables migration, if a high priority process preempts a task that holds the lock, and then the high prio task starts spinning waiting for that lock to release, the lower priority process will never get to run to release it. The cpu_chill() doesn't help. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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