From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751993AbaLIG0Q (ORCPT ); Tue, 9 Dec 2014 01:26:16 -0500 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:37891 "EHLO e06smtp12.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750739AbaLIG0P (ORCPT ); Tue, 9 Dec 2014 01:26:15 -0500 Date: Tue, 9 Dec 2014 07:26:10 +0100 From: Heiko Carstens To: Thomas Gleixner , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH] softirq/preempt: add missing current->preempt_disable_ip update Message-ID: <20141209062610.GC4362@osiris> References: <20141124141619.GB3738@osiris> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141124141619.GB3738@osiris> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14120906-0009-0000-0000-0000024D7541 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 24, 2014 at 03:16:19PM +0100, Heiko Carstens wrote: > While debugging some "sleeping function called from invalid context" bug I > realized that the debug message "Preemption disabled at:" pointed to an > incorrect function. > In particular if the function/action that disabled preemption was > spin_lock_bh() then current->preempt_disable_ip won't be updated. > > The reason for this is that __local_bh_disable_ip() will increase > preempt_count manually instead of calling preempt_count_add(), which > would handle the update correctly. > It look like the manual handling was done to work around some lockdep issue. > > So add the missing update of current->preempt_disable_ip to > __local_bh_disable_ip() as well. > > Signed-off-by: Heiko Carstens > --- > kernel/softirq.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/kernel/softirq.c b/kernel/softirq.c > index 501baa9ac1be..edd51027e3ab 100644 > --- a/kernel/softirq.c > +++ b/kernel/softirq.c > @@ -114,8 +114,13 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) > trace_softirqs_off(ip); > raw_local_irq_restore(flags); > > - if (preempt_count() == cnt) > - trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); > + if (preempt_count() == cnt) { > + unsigned long ip = get_parent_ip(CALLER_ADDR1); > +#ifdef CONFIG_DEBUG_PREEMPT > + current->preempt_disable_ip = ip; > +#endif > + trace_preempt_off(CALLER_ADDR0, ip); > + } > } > EXPORT_SYMBOL(__local_bh_disable_ip); > #endif /* CONFIG_TRACE_IRQFLAGS */ *ping*