Re: [PATCH] rwsem-spinlock: let rwsem write lock stealable

[Ingo Molnar <mingo@kernel.org>]

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* Yuanhan Liu <yuanhan.liu@linux.intel.com> wrote:

> On Thu, Jan 31, 2013 at 02:12:28PM +0100, Ingo Molnar wrote:
> > 
> > * Yuanhan Liu <yuanhan.liu@linux.intel.com> wrote:
> > 
> > > BTW, mind to tell a nice test case for mmap_sem?
> > 
> > this one was write-hitting on mmap_sem pretty hard, last I 
> > checked:
> > 
> >   http://people.redhat.com/mingo/threaded-mmap-stresstest/
> 
> Thanks!
> 
> Is there any pass condition? I tested a while, at least I 
> found no oops or any noisy from dmesg output. Is that OK?

Yeah, not crashing and not hanging is the expected behavior.

> Well, sometimes, it will quit peacefully. Sometimes it will 
> not. ps -eo 'pid, state,wchan,comm' shows that it is sleeping 
> at futex_wait_queue_me().
> 
> NOTE: this happens both with or w/o this patch. Thus it may 
> not an issue introduced by this patch?

hm, that's unexpected - it's expected to loop infinitely. I have 
a newer version (attached) - is that exiting too?

Maybe this triggers spuriously:

        if (!info->si_addr)
                raise(SIGABRT); /* Allow GDB backtrace */

although then you should see the SIGABRT as an irregular exit 
IIRC.

Thanks,

	Ingo

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