From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757008AbcAZCgN (ORCPT ); Mon, 25 Jan 2016 21:36:13 -0500 Received: from mail-ob0-f171.google.com ([209.85.214.171]:36748 "EHLO mail-ob0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756180AbcAZCgK (ORCPT ); Mon, 25 Jan 2016 21:36:10 -0500 Date: Mon, 25 Jan 2016 19:36:07 -0700 From: Jeff Merkey To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Don Zickus , Ulrich Obergfell , Aaron Tomlin , Michal Hocko , Frederic Weisbecker , Tejun Heo , Hidehiro Kawai , Chris Metcalf Subject: [PATCH] Add hard/soft lockup debugger entry points Message-ID: <20160126023607.GA5405@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 This patch adds an export which can be set by system debuggers to direct the hard lockup and soft lockup detector to trigger an INT3 exception and enter a debugger if one is active. It is assumed that if someone sets this variable, then an int3 handler of some sort will be actively loaded or registered via the notify die handler chain. This addition is extremely useful for debugging hard and soft lockups real time and quickly from a console debugger. Signed-off-by: Jeff Merkey --- kernel/watchdog.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index b3ace6e..f927722 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -108,6 +108,9 @@ static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); #endif static unsigned long soft_lockup_nmi_warn; +int debug_watchdog_lockups; +EXPORT_SYMBOL_GPL(debug_watchdog_lockups); + /* boot commands */ /* * Should we panic when a soft-lockup or hard-lockup occurs: @@ -358,6 +361,9 @@ static void watchdog_overflow_callback(struct perf_event *event, else dump_stack(); + if (debug_watchdog_lockups) + __asm__ __volatile__ ("int $0x03"); + /* * Perform all-CPU dump only once to avoid multiple hardlockups * generating interleaving traces @@ -478,6 +484,9 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) else dump_stack(); + if (debug_watchdog_lockups) + __asm__ __volatile__ ("int $0x03"); + if (softlockup_all_cpu_backtrace) { /* Avoid generating two back traces for current * given that one is already made above -- 1.8.3.1