Re: sem_lock() vs qspinlocks

[Peter Zijlstra]

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*.. OK, lemme have a harder look at this semaphore
code.