From: Jason Low <jason.low2@hpe.com>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: jason.low2@hp.com, Waiman Long <waiman.long@hpe.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Terry Rudd <terry.rudd@hpe.com>,
Scott J Norton <scott.norton@hpe.com>
Subject: Re: [PATCH] locking/mutex: Set and clear owner using WRITE_ONCE()
Date: Mon, 23 May 2016 14:49:55 -0700 [thread overview]
Message-ID: <1464040195.2519.5.camel@j-VirtualBox> (raw)
In-Reply-To: <20160523213123.c5qdhz23xy5ziqik@linux-uzut.site>
On Mon, 2016-05-23 at 14:31 -0700, Davidlohr Bueso wrote:
> On Mon, 23 May 2016, Jason Low wrote:
>
> >On Fri, 2016-05-20 at 18:00 -0700, Davidlohr Bueso wrote:
> >> On Fri, 20 May 2016, Waiman Long wrote:
> >>
> >> >I think mutex-debug.h also needs similar changes for completeness.
> >>
> >> Maybe, but given that with debug the wait_lock is unavoidable, doesn't
> >> this send the wrong message?
> >
> >The mutex_set_owner() and mutex_clear_owner() can still get called in
> >the fastpath without the wait_lock for the debug case too correct?
>
> The fastpath is a nop, see mutex-null:
>
> #define __mutex_fastpath_lock(count, fail_fn) fail_fn(count)
Oh right, so then the mutex_set_owner() call in mutex_lock() doesn't
really matter. I'll update the patch to remove the use of WRITE_ONCE for
the debug case then, and add the comments about why it is different as
suggested.
Thanks,
Jason
prev parent reply other threads:[~2016-05-23 21:50 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-19 22:23 [PATCH] locking/mutex: Set and clear owner using WRITE_ONCE() Jason Low
2016-05-20 1:19 ` Davidlohr Bueso
2016-05-20 20:27 ` Waiman Long
2016-05-20 22:09 ` Jason Low
2016-05-21 1:00 ` Davidlohr Bueso
2016-05-21 4:09 ` Waiman Long
2016-05-23 20:40 ` Jason Low
2016-05-23 21:31 ` Davidlohr Bueso
2016-05-23 21:49 ` Jason Low [this message]
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