linux-kernel - Re: [patch][rfc] x86, mutex: non-atomic unlock (and a rant)

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Message-ID: <20091102180959.GC10072@lenovo>
Date:	Mon, 2 Nov 2009 21:09:59 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [patch][rfc] x86, mutex: non-atomic unlock (and a rant)

[Cyrill Gorcunov - Mon, Nov 02, 2009 at 07:46:26PM +0300]
| 
| The other option could be that we put two mem-write operations
| like
| 	int tmp;
| 	atomic_set(&lock->count, 1);
| 	tmp = lock->waiters;
| 	rmb();
| 	lock->waiters = tmp;
| 	if (unlikely(lock->waiters))
| 		fail_fn(lock);
| 
| Which should work faster then cpuid (and we have to be sure somehow
| that gcc doesn't suppress this redundant operations).
|

And which has nothing to do with OoO mem-read, and wouldn't
work. Sorry for noise.
 
	-- Cyrill
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