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From: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Howells <dhowells@redhat.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	serue@us.ibm.com, viro@zeniv.linux.org.uk,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Nick Piggin <nickpiggin@yahoo.com.au>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] It may not be assumed that wake_up(), finish_wait() and co. imply a memory barrier
Date: Thu, 23 Apr 2009 23:24:34 +0200	[thread overview]
Message-ID: <20090423212434.GA20556@elte.hu> (raw)
In-Reply-To: <alpine.LFD.2.00.0904231410590.3101@localhost.localdomain>


* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Thu, 23 Apr 2009, David Howells wrote:
> > 
> > Well, Ingo's point is it could be left up to the caller of 
> > wake_up() to supply the barrier:

Well, i mainly reacted to your documentation patch which was 
incorrect as it said wake-up implies a _FULL_ memory barrier.

I also suggested that lockless code should have its barriers clearly 
documented and they should not really rely on kernel facilities 
acting as memory barriers.

Then i also suggested that maybe in the future we could remove the 
smp_wmb() from try_to_wake_up(). That was just an afterthought, and 
a rather stupid one at that, as Linus quickly noted :-)

	Ingo

  reply	other threads:[~2009-04-23 21:25 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-04-13 18:17 [PATCH] slow_work_thread() should do the exclusive wait Oleg Nesterov
2009-04-13 19:03 ` Trond Myklebust
2009-04-13 19:14   ` Oleg Nesterov
2009-04-13 21:40   ` David Howells
2009-04-13 21:48     ` Oleg Nesterov
2009-04-13 21:57       ` Trond Myklebust
2009-04-13 22:24         ` Oleg Nesterov
2009-04-15 23:27           ` Andrew Morton
2009-04-16  9:10             ` David Howells
2009-04-16 14:33               ` Oleg Nesterov
2009-04-22 13:37                 ` [PATCH] Document that wake_up(), complete() and co. imply a full memory barrier David Howells
2009-04-22 13:51                   ` Ingo Molnar
2009-04-22 14:39                     ` Oleg Nesterov
2009-04-22 14:56                       ` Ingo Molnar
2009-04-22 15:07                         ` Oleg Nesterov
2009-04-22 15:12                     ` David Howells
2009-04-22 15:19                       ` Ingo Molnar
2009-04-22 16:23                       ` David Howells
2009-04-22 17:57                         ` Ingo Molnar
2009-04-23 16:32                           ` [PATCH] It may not be assumed that wake_up(), finish_wait() and co. imply a " David Howells
2009-04-23 16:55                             ` Oleg Nesterov
2009-04-24 11:46                               ` David Howells
2009-04-24 15:08                                 ` Paul E. McKenney
2009-04-24 17:08                                   ` Oleg Nesterov
2009-04-24 17:43                                     ` Paul E. McKenney
2009-04-24 17:48                                   ` David Howells
2009-04-24 18:06                                     ` Paul E. McKenney
2009-04-28 10:18                                       ` David Howells
2009-04-28 13:00                                         ` Paul E. McKenney
2009-04-24 17:28                                 ` Oleg Nesterov
2009-04-24 17:53                                   ` David Howells
2009-04-24 18:30                                     ` Oleg Nesterov
2009-04-23 17:07                             ` Linus Torvalds
2009-04-23 20:35                               ` David Howells
2009-04-23 21:12                                 ` Linus Torvalds
2009-04-23 21:24                                   ` Ingo Molnar [this message]
2009-04-23 16:36                           ` [PATCH] Document that wake_up(), complete() and co. imply a full " Oleg Nesterov
2009-04-23 20:37                             ` David Howells
2009-04-23 16:00             ` [PATCH] slow_work_thread() should do the exclusive wait David Howells
2009-04-23 16:18               ` Oleg Nesterov
2009-04-13 21:35 ` David Howells

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