From: Ingo Molnar <mingo@elte.hu>
To: Joel Schopp <jschopp@austin.ibm.com>
Cc: Linus Torvalds <torvalds@osdl.org>,
lkml <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@osdl.org>,
Arjan van de Ven <arjan@infradead.org>,
Nicolas Pitre <nico@cam.org>,
Jes Sorensen <jes@trained-monkey.org>,
Al Viro <viro@ftp.linux.org.uk>, Oleg Nesterov <oleg@tv-sign.ru>,
David Howells <dhowells@redhat.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Christoph Hellwig <hch@infradead.org>, Andi Kleen <ak@suse.de>,
Russell King <rmk+lkml@arm.linux.org.uk>,
Anton Blanchard <anton@samba.org>,
PPC64-dev <linuxppc64-dev@ozlabs.org>
Subject: Re: [patch 00/21] mutex subsystem, -V14
Date: Fri, 6 Jan 2006 00:42:22 +0100 [thread overview]
Message-ID: <20060105234222.GA11474@elte.hu> (raw)
In-Reply-To: <43BDAD8A.60108@austin.ibm.com>
* Joel Schopp <jschopp@austin.ibm.com> wrote:
> > Shouldn't you make that "isync" dependent on SMP too? UP doesn't
> > need it, since DMA will never matter, and interrupts are precise.
>
> I think the isync is necessary to keep heavily out of order processors
> from getting ahead of themselves even on UP. Scanning back through
> the powerpc spinlock code they seem to take the same view there as
> well.
the asm/spinlock.h ops are only built on SMP kernels. mutex.h is for
both UP and SMP. On UP you should need no synchronization, because the
only way another context could interfere with your critical section is
by getting interrupted, and interrupts are fully synchronizing, right?
On UP the only synchronization needed is when a device reads/writes
memory in parallel to the CPU.
Ingo
next prev parent reply other threads:[~2006-01-05 23:42 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-04 14:41 [patch 00/21] mutex subsystem, -V14 Ingo Molnar
2006-01-04 23:45 ` Joel Schopp
2006-01-05 2:38 ` Nicolas Pitre
2006-01-05 2:51 ` Linus Torvalds
2006-01-05 3:21 ` Nick Piggin
2006-01-05 3:39 ` Anton Blanchard
2006-01-05 18:04 ` Jesse Barnes
2006-01-05 14:40 ` Ingo Molnar
2006-01-05 16:21 ` Linus Torvalds
2006-01-05 22:03 ` Ingo Molnar
2006-01-05 22:17 ` Linus Torvalds
2006-01-05 22:43 ` Ingo Molnar
2006-01-06 3:49 ` Keith Owens
2006-01-06 7:34 ` Denis Vlasenko
2006-01-05 14:35 ` Ingo Molnar
2006-01-05 16:42 ` Joel Schopp
2006-01-05 22:21 ` Ingo Molnar
2006-01-05 23:06 ` Joel Schopp
2006-01-05 23:26 ` Linus Torvalds
2006-01-05 23:36 ` Joel Schopp
2006-01-05 23:42 ` Ingo Molnar [this message]
2006-01-06 0:29 ` Olof Johansson
2006-01-07 17:49 ` PowerPC fastpaths for mutex subsystem Joel Schopp
2006-01-07 22:37 ` Andrew Morton
2006-01-08 7:43 ` Anton Blanchard
2006-01-08 8:00 ` Andrew Morton
2006-01-08 8:23 ` Anton Blanchard
2006-01-09 11:13 ` David Howells
2006-01-08 9:48 ` Ingo Molnar
2006-01-10 22:31 ` Joel Schopp
2006-01-10 23:09 ` Ingo Molnar
2006-01-11 10:52 ` Ingo Molnar
2006-01-11 17:44 ` Joel Schopp
2006-01-08 10:43 ` Ingo Molnar
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