From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751707AbdJSCAr (ORCPT ); Wed, 18 Oct 2017 22:00:47 -0400 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:46354 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751570AbdJSCAp (ORCPT ); Wed, 18 Oct 2017 22:00:45 -0400 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Thu, 19 Oct 2017 11:00:33 +0900 From: Byungchul Park To: Thomas Gleixner Cc: Ingo Molnar , 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: <20171019020033.GG32368@X58A-UD3R> References: <1508318006-2090-1-git-send-email-byungchul.park@lge.com> <20171018133019.cwfhnt46pvhirt57@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 18, 2017 at 03:36:05PM +0200, Thomas Gleixner wrote: > On Wed, 18 Oct 2017, Ingo Molnar wrote: > > * 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. > > That makes sense. Like we have with debug objects: > DEBUG_OBJECTS_ENABLE_DEFAULT. Thank you very much for the suggestion. I will work for it. > Which reminds me that I wanted to convert them to static_key so they are > zero overhead when disabled. Sigh, why are todo lists growth only? > > Thanks, > > tglx