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SubjectRe: sem_lock() vs qspinlocks
On Fri, May 20, 2016 at 12:09:01PM +0200, Ingo Molnar wrote:
>
> * Peter Zijlstra <peterz@infradead.org> wrote:
>
> > On Fri, May 20, 2016 at 10:30:08AM +0200, Peter Zijlstra wrote:
> > > On Thu, May 19, 2016 at 10:39:26PM -0700, Davidlohr Bueso wrote:
> > > > Specifically
> > > > for the 'cascade_cond' and 'cascade_flock' programs, which exhibit hangs in libc's
> > > > semop() blocked waiting for zero.
> > >
> > > OK; so I've been running:
> > >
> > > while :; do
> > > bin/cascade_cond -E -C 200 -L -S -W -T 200 -I 2000000 ;
> > > bin/cascade_flock -E -C 200 -L -S -W -P 200 -I 5000000 ;
> > > done
> > >
> > > for a few minutes now and its not stuck and my machine didn't splat.
> > >
> > > Am I not doing it right?
> >
> > Hooray, it went *bang*..
>
> I suspect a required step was to post about failure to reproduce!
>

It is known that the bug is both intermittent and not all machines can
reproduce the problem. If it fails to reproduce, it's not necessarily a
methodology error and can simply be a function of luck.

--
Mel Gorman
SUSE Labs

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