From: David Howells <dhowells@redhat.com>
To: Sergei Organov <osv@javad.com>
Cc: David Howells <dhowells@redhat.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Document Linux's memory barriers [try #4]
Date: Tue, 14 Mar 2006 20:31:57 +0000 [thread overview]
Message-ID: <31016.1142368317@warthog.cambridge.redhat.com> (raw)
In-Reply-To: <878xrecypp.fsf@javad.com>
Sergei Organov <osv@javad.com> wrote:
> "You can prevent an `asm' instruction from being deleted by writing the
> keyword `volatile' after the `asm'. [...]
> The `volatile' keyword indicates that the instruction has important
> side-effects. GCC will not delete a volatile `asm' if it is reachable.
> (The instruction can still be deleted if GCC can prove that
> control-flow will never reach the location of the instruction.) *Note
> that even a volatile `asm' instruction can be moved relative to other
> code, including across jump instructions.*"
Ummm... If "asm volatile" statements don't form compiler barriers, then how do
you specify a compiler barrier? Or is that what the "memory" bit in:
#define barrier() __asm__ __volatile__("": : :"memory")
does?
David
next prev parent reply other threads:[~2006-03-14 20:32 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-09 20:29 [PATCH] Document Linux's memory barriers [try #4] David Howells
2006-03-09 23:34 ` Paul Mackerras
2006-03-09 23:45 ` Michael Buesch
2006-03-09 23:56 ` Linus Torvalds
2006-03-10 0:07 ` Michael Buesch
2006-03-10 0:48 ` Alan Cox
2006-03-10 0:54 ` Paul Mackerras
2006-03-10 15:19 ` David Howells
2006-03-11 0:01 ` Paul Mackerras
2006-03-10 5:28 ` Nick Piggin
2006-03-15 11:10 ` David Howells
2006-03-15 11:51 ` Nick Piggin
2006-03-15 13:47 ` David Howells
2006-03-15 23:21 ` Nick Piggin
2006-03-12 17:15 ` Eric W. Biederman
2006-03-14 21:26 ` David Howells
2006-03-14 21:26 ` David Howells
2006-03-14 21:48 ` Paul Mackerras
2006-03-14 21:48 ` Paul Mackerras
2006-03-14 23:59 ` David Howells
2006-03-14 23:59 ` David Howells
2006-03-15 0:20 ` Linus Torvalds
2006-03-15 1:19 ` David Howells
2006-03-15 1:47 ` Linus Torvalds
2006-03-15 1:25 ` Nick Piggin
2006-03-15 0:54 ` Paul Mackerras
2006-03-15 0:54 ` Paul Mackerras
2006-03-13 12:32 ` Sergei Organov
2006-03-14 20:31 ` David Howells [this message]
2006-03-14 21:11 ` linux-os (Dick Johnson)
2006-03-15 9:09 ` Sergei Organov
2006-03-15 9:04 ` Sergei Organov
2006-03-14 20:35 ` David Howells
2006-03-15 9:11 ` Sergei Organov
2006-03-15 14:23 ` [PATCH] Document Linux's memory barriers [try #5] David Howells
[not found] ` <20060315200956.4a9e2cb3.akpm@osdl.org>
2006-03-16 11:50 ` David Howells
2006-03-16 17:18 ` Linus Torvalds
2006-03-17 1:20 ` Nick Piggin
2006-03-16 23:17 ` Paul E. McKenney
2006-03-16 23:55 ` Linus Torvalds
2006-03-17 1:29 ` Paul E. McKenney
2006-03-17 5:32 ` Linus Torvalds
2006-03-17 6:23 ` Paul E. McKenney
2006-03-23 18:34 ` David Howells
2006-03-23 18:34 ` David Howells
2006-03-23 19:28 ` Linus Torvalds
2006-03-23 19:28 ` Linus Torvalds
2006-03-23 22:26 ` Paul E. McKenney
2006-03-23 22:26 ` Paul E. McKenney
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