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From: Paul Mackerras <paulus@samba.org>
To: "Martin J. Bligh" <Martin.Bligh@us.ibm.com>
Cc: Peter Rival <frival@zk3.dec.com>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>,
	torvalds@transmeta.com, linux-kernel@vger.kernel.org,
	trini@kernel.crashing.org, benh@kernel.crashing.org
Subject: Re: [PATCH] change name of rep_nop
Date: Sat, 6 Oct 2001 11:40:57 +1000 (EST)	[thread overview]
Message-ID: <15294.24873.866942.423260@cargo.ozlabs.ibm.com> (raw)
In-Reply-To: <1573466920.1002300846@mbligh.des.sequent.com>
In-Reply-To: <15294.16913.2117.383987@cargo.ozlabs.ibm.com> <1573466920.1002300846@mbligh.des.sequent.com>

Martin J. Bligh writes:

> There *is* a race on x86 - the problem is that the primary cpu can 
> get to reschedule_idle before the secondarys have done init_idle.
> I'm not claiming the way I fixed it is beautiful, but the race definitely
> exists (I hit it) and the patch makes the problem go away. 

I meant that there isn't a race on x86 in pre4, now that we are using
your patch.  I didn't mean to say that there wasn't a race on x86
before your patch went in.

There is a race on PPC with your patch, but I can fix that by removing
the init_idle() call from smp_callin() in arch/ppc/kernel/smp.c.
At a quick glance it looks like alpha and sparc (sun4m) may have the
same problem since they also call init_idle before waiting for
smp_commence() (or smp_threads_ready != 0).

> Sounds like rep_nop was the wrong way to spin - aplogies.

Well it was just that the name was a bit x86-centric, and a bit
non-obvious, even to people who know a bit of x86 assembly (one could
be forgiven for thinking that rep nop was a slow way to set CX to 0).

Paul.

  parent reply	other threads:[~2001-10-06  1:41 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-10-05 10:46 Paul Mackerras
2001-10-05 14:37 ` Alan Cox
2001-10-05 18:06   ` Peter Rival
2001-10-05 23:28   ` Paul Mackerras
2001-10-05 23:54     ` Martin J. Bligh
2001-10-06  1:40     ` Paul Mackerras [this message]
2001-10-08 19:27       ` Peter Rival
2001-10-08 22:36       ` David Woodhouse
2001-10-08 22:49         ` Alan Cox
2001-10-08 23:06         ` David Woodhouse
2001-10-08 23:42           ` David Woodhouse
2001-10-08 23:46           ` David S. Miller
2001-10-08 23:08         ` David S. Miller
2001-10-08 23:46         ` Linus Torvalds
2001-10-09  0:03           ` David Woodhouse
2001-10-08 22:46       ` David S. Miller
2001-10-08 23:16         ` Alan Cox
2001-10-08 23:24           ` Dave Jones
2001-10-08 23:33             ` Alan Cox
2001-10-09  5:01             ` George Greer
2001-10-08 23:30           ` David S. Miller
2001-10-09 10:33           ` Benjamin Herrenschmidt
2001-10-09 11:30             ` Keith Owens
2001-10-09 12:13               ` Benjamin Herrenschmidt
2001-10-09 12:15               ` Alan Cox
2001-10-09  8:51 Etienne Lorrain
2001-10-09 11:30 ` Alan Cox

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