From mboxrd@z Thu Jan 1 00:00:00 1970 From: john.hubbard@gmail.com Subject: [PATCH] watchdog: Fix a watchdog crash in some configurations Date: Mon, 4 May 2015 16:17:07 -0700 Message-ID: <1430781427-31318-1-git-send-email-jhubbard@nvidia.com> Return-path: Received: from mail-pd0-f174.google.com ([209.85.192.174]:36214 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750973AbbEDXTT (ORCPT ); Mon, 4 May 2015 19:19:19 -0400 Received: by pdea3 with SMTP id a3so176520424pde.3 for ; Mon, 04 May 2015 16:19:18 -0700 (PDT) Sender: linux-next-owner@vger.kernel.org List-ID: To: Chris Metcalf Cc: Don Zickus , Ingo Molnar , Ulrich Obergfell , Thomas Gleixner , Peter Zijlstra , Andrew Morton , Stephen Rothwell , linux-next@vger.kernel.org, John Hubbard From: John Hubbard Commit 8fcf2cc768acd845c1fed837bf9cfe2d7106336d in linux-next introduced a regression in some configurations. Specifically, with CONFIG_NO_HZ_FULL set, and CONFIG_NO_HZ_FULL_ALL *not* set, the kernel will crash in lockup_detector_init(), due to a NULL tick_nohz_full_mask pointer. This is because the above commit uses tick_nohz_full_mask (in lockup_detector_init), if CONFIG_NO_HZ_FULL is set, but tick_nohz_full_mask only gets allocated if either: a) CONFIG_NO_HZ_FULL_ALL is set, or b) Someone passes in nohz_full= on the boot args line. To correct this, change lockup_detector_init so that it does a runtime check (in addition to the ifdef check). This now matches the way most of the other CONFIG_NO_HZ_FULL code does it's checking. This fix is a little simpler than my original proposed fix, thanks to Chris Metcalf for that. Signed-off-by: John Hubbard --- kernel/watchdog.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 40fda2f..910d73f 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -921,10 +921,14 @@ void __init lockup_detector_init(void) set_sample_period(); #ifdef CONFIG_NO_HZ_FULL - if (!cpumask_empty(tick_nohz_full_mask)) - pr_info("Disabling watchdog on nohz_full cores by default\n"); - cpumask_andnot(&watchdog_cpumask, cpu_possible_mask, - tick_nohz_full_mask); + if (tick_nohz_full_enabled()) { + if (!cpumask_empty(tick_nohz_full_mask)) + pr_info("Disabling watchdog on nohz_full cores by default\n"); + cpumask_andnot(&watchdog_cpumask, cpu_possible_mask, + tick_nohz_full_mask); + } + else + cpumask_copy(&watchdog_cpumask, cpu_possible_mask); #else cpumask_copy(&watchdog_cpumask, cpu_possible_mask); #endif -- 2.3.7