linux-kernel - Re: sem_lock() vs qspinlocks

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Date:	Fri, 20 May 2016 12:09:01 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Davidlohr Bueso <dave@...olabs.net>, manfred@...orfullife.com,
	Waiman.Long@....com, torvalds@...ux-foundation.org,
	ggherdovich@...e.com, mgorman@...hsingularity.net,
	linux-kernel@...r.kernel.org
Subject: Re: sem_lock() vs qspinlocks


* Peter Zijlstra <peterz@...radead.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!

	Ingo