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From: Miklos Szeredi <miklos@szeredi.hu>
To: dhowells@redhat.com
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: memory barrier question
Date: Wed, 15 Sep 2010 16:36:39 +0200	[thread overview]
Message-ID: <E1Ovt6F-0005CS-RU@pomaz-ex.szeredi.hu> (raw)

Hi,

I'm trying to understand memory barriers but not quite succeeding.

Consider the following example:

Start:
	p = NULL;
	x = 0;

CPU1:
	atomic_inc(&x);
	p = &x;

CPU2:
	if (p)
		z = atomic_read(p);

Is it possible to end up with z == 0?  What if there's a lock/unlock
before setting "p"?  What if there's a write barrier before setting
"p"?

Thanks,
Miklos

             reply	other threads:[~2010-09-15 14:36 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-15 14:36 Miklos Szeredi [this message]
2010-09-15 19:12 ` Rafael J. Wysocki
2010-09-16 11:55 ` David Howells
2010-09-16 13:42   ` Miklos Szeredi
2010-09-16 14:30   ` David Howells
2010-09-16 15:03     ` Paul E. McKenney
2010-09-16 16:06       ` Miklos Szeredi
2010-09-16 16:37         ` Paul E. McKenney
2010-09-16 16:56           ` Miklos Szeredi
2010-09-16 17:09             ` James Bottomley
2010-09-16 17:17               ` Miklos Szeredi
2010-09-16 17:40                 ` James Bottomley
2010-09-17 21:49                 ` Benjamin Herrenschmidt
2010-09-17 23:12                   ` Paul E. McKenney
2010-09-19  2:47                     ` Benjamin Herrenschmidt
2010-09-19 15:26                       ` Paul E. McKenney
2010-09-19 20:15                         ` Miklos Szeredi
2010-09-19 21:59                           ` Paul E. McKenney
2010-09-20  0:58                             ` James Bottomley
2010-09-20  1:29                               ` Paul E. McKenney
2010-09-20 16:01                                 ` Miklos Szeredi
2010-09-20 18:25                                   ` Paul E. McKenney
2010-09-20 18:57                                     ` Paul E. McKenney
2010-09-20 20:26                                     ` Michael Cree
2010-09-20 20:40                                       ` Paul E. McKenney
2010-09-21 14:59                                         ` Paul E. McKenney
2010-09-22 18:41                                           ` Paul E. McKenney
2010-09-18  1:12                   ` Alan Cox
2010-09-16 16:50         ` Jamie Lokier
2010-09-16 16:18   ` Peter Zijlstra
2010-09-16 17:59   ` David Howells
2010-09-20 10:34 George Spelvin
2010-10-29 13:23 Memory " Tetsuo Handa
2010-10-29 15:09 ` Paul E. McKenney
2010-10-30  5:48   ` Tetsuo Handa
2010-10-30  6:11     ` Eric Dumazet
2010-10-30 12:40       ` Tetsuo Handa

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