Re: 3.4.4-rt13: btrfs + xfstests 006 = BOOM.. and a bonus rt_mutexdeadlock report for absolutely free!

[Mike Galbraith]

On Mon, 2012-07-16 at 18:26 +0200, Mike Galbraith wrote: 
> On Mon, 2012-07-16 at 12:02 -0400, Steven Rostedt wrote: 
> > On Mon, 2012-07-16 at 04:02 +0200, Mike Galbraith wrote:
> > 
> > > > Great, thanks!  I got stuck in bug land on Friday.  You mentioned
> > > > performance problems earlier on Saturday, did this improve performance?
> > > 
> > > Yeah, the read_trylock() seems to improve throughput.  That's not
> > > heavily tested, but it certainly looks like it does.  No idea why.
> > 
> > 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).

-Mike

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