From: Peter Zijlstra <peterz@infradead.org>
To: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Chris Wilson <chris@chris-wilson.co.uk>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] mutex: Remove ww_ctx unlikely() from __mutex_lock_common()
Date: Thu, 19 Jan 2017 17:42:52 +0100 [thread overview]
Message-ID: <20170119164252.GL6485@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20170119085441.09168f48@gandalf.local.home>
On Thu, Jan 19, 2017 at 08:54:41AM -0500, Steven Rostedt (VMware) wrote:
> I added a comment stating that the branch should be unlikely, but due
> to the intel drm logic, it currently isn't. Then if drm changes in the
> future, we could then try it again.
I really don't see the point here. The unlikely() also conveys this is
not a fast path branch and that is still true, regardsless of what
runtime does.
Also, the patch wouldn't apply even if I were so inclined.
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index a70b90d..577bb74 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -513,7 +513,11 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
>
> if (use_ww_ctx) {
> struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
> - if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
> + /*
> + * This really should be an unlikely() but currently
> + * the intel drm makes this a very likely case.
> + */
> + if (ww_ctx == READ_ONCE(ww->ctx))
> return -EALREADY;
> }
>
next prev parent reply other threads:[~2017-01-19 20:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-18 20:58 __mutex_lock_common() unlikely very likely Steven Rostedt
2017-01-19 8:55 ` Chris Wilson
2017-01-19 13:32 ` Steven Rostedt
2017-01-19 13:54 ` [PATCH] mutex: Remove ww_ctx unlikely() from __mutex_lock_common() Steven Rostedt (VMware)
2017-01-19 16:42 ` Peter Zijlstra [this message]
2017-01-19 16:50 ` Steven Rostedt
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