linux-kernel - Re: [REPOST-v2] sched: Prevent wakeup to enter critical section needlessly

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Message-ID: <20121121134747.261c426a@pyramind.ukuu.org.uk>
Date:	Wed, 21 Nov 2012 13:47:47 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Ivo Sieben <meltedpianoman@...il.com>
Cc:	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, linux-serial@...r.kernel.org,
	Alan Cox <alan@...ux.intel.com>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [REPOST-v2] sched: Prevent wakeup to enter critical section
 needlessly

> But we try to understand your fault scenario: How can the LOAD leak
> into the critical section? As far as we understand the spin_unlock()
> function also contains a memory barrier to prevent such a reordering
> from happening.

It does - it would be very interesting for someone to look at the assembly
if this is making a difference.

Alan
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