From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754056AbdJRNaa (ORCPT ); Wed, 18 Oct 2017 09:30:30 -0400 Received: from mail-wr0-f193.google.com ([209.85.128.193]:56901 "EHLO mail-wr0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753903AbdJRNaX (ORCPT ); Wed, 18 Oct 2017 09:30:23 -0400 X-Google-Smtp-Source: ABhQp+TpOuFelckN+OwX/Wv0YMjkeVbZkSBLeraufXrpq0gbbaXxd5gu/PwrhBJYpoKA9HUcl3eefQ== Date: Wed, 18 Oct 2017 15:30:19 +0200 From: Ingo Molnar To: Thomas Gleixner Cc: Byungchul Park , peterz@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@lge.com Subject: Re: [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make it not unwind as default Message-ID: <20171018133019.cwfhnt46pvhirt57@gmail.com> References: <1508318006-2090-1-git-send-email-byungchul.park@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Thomas Gleixner wrote: > On Wed, 18 Oct 2017, Byungchul Park wrote: > > #ifdef CONFIG_LOCKDEP_CROSSRELEASE > > +#ifdef CONFIG_CROSSRELEASE_STACK_TRACE > > #define MAX_XHLOCK_TRACE_ENTRIES 5 > > +#else > > +#define MAX_XHLOCK_TRACE_ENTRIES 1 > > +#endif > > > > /* > > * This is for keeping locks waiting for commit so that true dependencies > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > > index e36e652..5c2ddf2 100644 > > --- a/kernel/locking/lockdep.c > > +++ b/kernel/locking/lockdep.c > > @@ -4863,8 +4863,13 @@ static void add_xhlock(struct held_lock *hlock) > > xhlock->trace.nr_entries = 0; > > xhlock->trace.max_entries = MAX_XHLOCK_TRACE_ENTRIES; > > xhlock->trace.entries = xhlock->trace_entries; > > +#ifdef CONFIG_CROSSRELEASE_STACK_TRACE > > xhlock->trace.skip = 3; > > save_stack_trace(&xhlock->trace); > > +#else > > + xhlock->trace.nr_entries = 1; > > + xhlock->trace.entries[0] = hlock->acquire_ip; > > +#endif > > Hmm. Would it be possible to have this switchable at boot time via a > command line parameter? So in case of a splat with no stack trace, one > could just reboot and set something like 'lockdep_fullstack' on the kernel > command line to get the full data without having to recompile the kernel. Yeah, and I'd suggest keeping the Kconfig option to default-enable that boot option as well - i.e. let's have both. Thanks, Ingo