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From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Davide Libenzi <davidel@xmailserver.org>
Cc: Linux Kernel List <linux-kernel@vger.kernel.org>
Subject: Re: scheduler: IRQs disabled over context switches
Date: Mon, 24 May 2004 00:33:08 +0100	[thread overview]
Message-ID: <20040524003308.B4818@flint.arm.linux.org.uk> (raw)
In-Reply-To: <Pine.LNX.4.58.0405231241450.512@bigblue.dev.mdolabs.com>; from davidel@xmailserver.org on Sun, May 23, 2004 at 04:04:39PM -0700

On Sun, May 23, 2004 at 04:04:39PM -0700, Davide Libenzi wrote:
> On Sun, 23 May 2004, Russell King wrote:
> > Not quite - look harder.  They use spin_unlock_irq in finish_arch_switch
> > rather than prepare_arch_switch.
> 
> Hmm, they do indeed. Hmm, if we release the rq lock before the ctx switch, 
> "prev" (the real one) will result not running since we already set 
> "rq->curr" to "next" (and we do not hold "prev->switch_lock").

We do hold prev->switch_lock - we hold it all the time that the thread
is running.  Consider what prepare_arch_switch() is doing - it's taking
the next threads switch_lock.  It only gets released _after_ we've
switched away from that thread.

So I think your analysis is flawed.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 PCMCIA      - http://pcmcia.arm.linux.org.uk/
                 2.6 Serial core

  reply	other threads:[~2004-05-23 23:33 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-05-23 16:43 Russell King
2004-05-23 18:59 ` Davide Libenzi
2004-05-23 19:38   ` Russell King
2004-05-23 23:04     ` Davide Libenzi
2004-05-23 23:33       ` Russell King [this message]
2004-05-24  0:27         ` Davide Libenzi
2004-05-24  8:37 ` Ingo Molnar
2004-05-24  6:41   ` Davide Libenzi
2004-05-24  9:05     ` Ingo Molnar
2004-05-24  7:10       ` Nick Piggin
2004-05-24  9:15         ` Ingo Molnar
2004-05-24 17:16       ` Davide Libenzi
2004-05-24 17:46         ` Davide Libenzi

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