From: Andi Kleen <andi@firstfloor.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Andi Kleen <andi@firstfloor.org>,
Ivo Sieben <meltedpianoman@gmail.com>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
linux-serial@vger.kernel.org, Alan Cox <alan@linux.intel.com>,
Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [REPOST] RFC: sched: Prevent wakeup to enter critical section needlessly
Date: Wed, 10 Oct 2012 16:02:49 +0200 [thread overview]
Message-ID: <20121010140249.GX16230@one.firstfloor.org> (raw)
In-Reply-To: <20121009151729.GA3521@redhat.com>
> wait_event:
>
> prepare_to_wait(wq) // takes wq->lock
>
> if (!CONDITION)
> schedule();
>
> Now,
>
> CONDITION = 1;
> wake_up(wq);
>
> at least need the full mb() before lits_empty().
You're right, but it would probably only matter for inlining with LTO
(if the LTO compiler ever decides to do that)
Without that a call should be always enough barrier in practice.
So yes I would add the mb, but most likely it will not make much
difference. Just make sure to comment it.
-Andi
next prev parent reply other threads:[~2012-10-10 14:02 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-24 13:06 [PATCH] " Ivo Sieben
2012-10-09 11:30 ` [REPOST] " Ivo Sieben
2012-10-09 13:37 ` Andi Kleen
2012-10-09 14:15 ` Peter Zijlstra
2012-10-09 15:17 ` Oleg Nesterov
2012-10-10 14:02 ` Andi Kleen [this message]
2012-10-18 8:30 ` [PATCH-v2] " Ivo Sieben
2012-10-25 10:12 ` [REPOST-v2] " Ivo Sieben
2012-11-19 7:30 ` Ivo Sieben
2012-11-19 10:20 ` Preeti U Murthy
2012-11-19 15:10 ` Oleg Nesterov
2012-11-19 15:34 ` Ivo Sieben
2012-11-19 15:49 ` Oleg Nesterov
2012-11-21 13:03 ` Ivo Sieben
2012-11-21 13:47 ` Alan Cox
2012-11-21 13:58 ` Oleg Nesterov
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