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
next prev parent 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 scheduler: IRQs disabled over context switches 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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