From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <benh@kernel.crashing.org>
Received: from gate.crashing.org (gate.crashing.org [63.228.1.57])
	(using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
	(Client did not present a certificate)
	by ozlabs.org (Postfix) with ESMTPS id E7091DDFF8
	for <linuxppc-dev@ozlabs.org>; Wed, 15 Oct 2008 22:37:42 +1100 (EST)
Subject: Re: [PROBLEM] Soft lockup on Linux 2.6.27, 2 patches, Cell/PPC64
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
In-Reply-To: <Pine.LNX.4.64.0810151135330.1133@vixen.sonytel.be>
References: <48F17DE6.106@gmail.com>
	<Pine.LNX.4.64.0810130945260.17287@vixen.sonytel.be>
	<Pine.LNX.4.64.0810141130340.16020@vixen.sonytel.be>
	<1224046194.8157.428.camel@pasglop>
	<Pine.LNX.4.64.0810151050330.1133@vixen.sonytel.be>
	<1224062907.8157.446.camel@pasglop>
	<Pine.LNX.4.64.0810151135330.1133@vixen.sonytel.be>
Content-Type: text/plain; charset=utf-8
Date: Wed, 15 Oct 2008 22:37:33 +1100
Message-Id: <1224070653.8157.452.camel@pasglop>
Mime-Version: 1.0
Cc: Linux/PPC Development <linuxppc-dev@ozlabs.org>,
	Aaron Tokhy <atokhy@gmail.com>
Reply-To: benh@kernel.crashing.org
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.ozlabs.org>
List-Unsubscribe: <https://ozlabs.org/mailman/options/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=unsubscribe>
List-Archive: <http://ozlabs.org/pipermail/linuxppc-dev>
List-Post: <mailto:linuxppc-dev@ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@ozlabs.org?subject=help>
List-Subscribe: <https://ozlabs.org/mailman/listinfo/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=subscribe>


> > Well, at the time of the sample, the other CPU indeed -seems- to be in
> > an IRQ disabled section yes. 
> 
> This is not really a sample. The hardirqs enable/disable is actually tracked
> using the TRACE_{EN,DIS}ABLE_INTS macros.

That's what I meant. IE. the hardirq state was updated by the stuck CPU
but sampled by the non-stuck one. ie. the non-stuck one could have
sampled a transcient value where it happened to have hard irq
disabled...

> For the decrementer, the interrupt code is generated by the
> STD_EXCEPTION_COMMON_LITE() macro.

Yeah, I know that :-)

> Aha, none of the PPC interrupt handlers actually us TRACE_ENABLE_INTS (they do
> use TRACE_DISABLE_INTS). So that's why it thinks decrementer_common disabled
> interrupts, without enabling them again...

Well, they aren't supposed to enable IRQs if they were disabled...

Ben.

> With kind regards,
> 
> Geert Uytterhoeven
> Software Architect
> 
> Sony Techsoft Centre Europe
> The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium
> 
> Phone:    +32 (0)2 700 8453
> Fax:      +32 (0)2 700 8622
> E-mail:   Geert.Uytterhoeven@sonycom.com
> Internet: http://www.sony-europe.com/
> 
> A division of Sony Europe (Belgium) N.V.
> VAT BE 0413.825.160 · RPR Brussels
> Fortis · BIC GEBABEBB · IBAN BE41293037680010