From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753797AbdJRNYI (ORCPT ); Wed, 18 Oct 2017 09:24:08 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:56551 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751524AbdJRNXj (ORCPT ); Wed, 18 Oct 2017 09:23:39 -0400 Date: Wed, 18 Oct 2017 15:23:32 +0200 (CEST) From: Thomas Gleixner To: Byungchul Park cc: peterz@infradead.org, mingo@kernel.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 In-Reply-To: <1508318006-2090-1-git-send-email-byungchul.park@lge.com> Message-ID: References: <1508318006-2090-1-git-send-email-byungchul.park@lge.com> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks, tglx