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

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Date:	Fri, 1 Feb 2013 10:16:28 +0800
From:	Yuanhan Liu <yuanhan.liu@...ux.intel.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Michel Lespinasse <walken@...gle.com>,
	linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>
Subject: Re: [PATCH] rwsem-spinlock: let rwsem write lock stealable

On Thu, Jan 31, 2013 at 10:18:18PM +0100, Ingo Molnar wrote:
> 
> * Yuanhan Liu <yuanhan.liu@...ux.intel.com> wrote:
> 
> > On Thu, Jan 31, 2013 at 02:12:28PM +0100, Ingo Molnar wrote:
> > > 
> > > * Yuanhan Liu <yuanhan.liu@...ux.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.

Good to know.

> 
> > 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.

Reall sorry about that. My bad. I modify the code a bit: removed the two
//, so that thread will exit after count > 1000000.

Sorry again :(

	--yliu

> 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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