Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764960AbYHEUxq (ORCPT ); Tue, 5 Aug 2008 16:53:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759376AbYHEUxi (ORCPT ); Tue, 5 Aug 2008 16:53:38 -0400 Received: from mtagate1.de.ibm.com ([195.212.29.150]:7678 "EHLO mtagate1.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758936AbYHEUxh (ORCPT ); Tue, 5 Aug 2008 16:53:37 -0400 From: Christian Borntraeger To: Alex Nixon Subject: Re: Spinlock recursion in hvc_poll Date: Tue, 5 Aug 2008 22:53:10 +0200 User-Agent: KMail/1.9.9 Cc: Jeremy Fitzhardinge , Linux Kernel Mailing List , Rusty Russell References: <48973E59.1000904@citrix.com> <48987DD8.8080009@citrix.com> <48989727.8090804@goop.org> In-Reply-To: <48989727.8090804@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200808052253.10285.borntraeger@de.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1646 Lines: 49 Am Dienstag, 5. August 2008 schrieb Jeremy Fitzhardinge: > Alex Nixon wrote: > >>> Well I say fixed - it just means I can proceed to a spinlock recursion > >>> BUG() 2 secs into the boot process, but it should be easier to track down > >>> with printks and a coherent stack dump at my disposal. > >>> > >>> > >> What's the backtrace on this? > >> > > > > I just turned DEBUG_SPINLOCKS back on to try catch this bug again, and it > > seems to occur (very roughly) 1/10 of the time, with nothing changing between > > runs. Ok, this is a guess, I dont fully understand the backtrace. request_irq tries to call the handler if the IRQ is shared. The irq handler calls hvc_poll and hvc_kill which might take the same spinlock. Can you test it this patch fixes the problem? Signed-off-by: Christian Borntraeger --- drivers/char/hvc_console.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) Index: linux-2.6/drivers/char/hvc_console.c =================================================================== --- linux-2.6.orig/drivers/char/hvc_console.c +++ linux-2.6/drivers/char/hvc_console.c @@ -322,10 +322,11 @@ static int hvc_open(struct tty_struct *t hp->tty = tty; + spin_unlock_irqrestore(&hp->lock, flags); + if (hp->ops->notifier_add) rc = hp->ops->notifier_add(hp, hp->data); - spin_unlock_irqrestore(&hp->lock, flags); /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/