Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758250Ab3ENQDQ (ORCPT ); Tue, 14 May 2013 12:03:16 -0400 Received: from mail-we0-f174.google.com ([74.125.82.174]:43325 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752342Ab3ENQDN (ORCPT ); Tue, 14 May 2013 12:03:13 -0400 From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Steven Rostedt , "Paul E. McKenney" , Andrew Morton , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Frederic Weisbecker Subject: [PATCH 1/2] nohz: Disable LOCKUP_DETECTOR when NO_HZ_FULL is enabled Date: Tue, 14 May 2013 18:02:51 +0200 Message-Id: <1368547372-21011-2-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1368547372-21011-1-git-send-email-fweisbec@gmail.com> References: <1368547372-21011-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1845 Lines: 51 From: Steven Rostedt Trying to test the nohz_full code, I was not able to get it to work. Finally I enabled the tick_stop tracepoint and it showed: tick_stop: success=no msg=perf events running I talked to Frederic Weisbecker about this and he informed me that perf is used by the lockup detector. I checked the code, and sure enough it is. As perf is always running when LOCKUP_DETECTOR is enabled, which will always disable nohz_full from working, instead of confusing users, disable LOCKUP_DETECTOR when NO_HZ_FULL is enabled. When perf is changed such that it does not prevent nohz_full from working, then we can and should remove this constraint. Signed-off-by: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Andrew Morton Cc: Thomas Gleixner Cc: H. Peter Anvin Cc: Peter Zijlstra Signed-off-by: Frederic Weisbecker --- lib/Kconfig.debug | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 566cf2b..1364d09 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -174,6 +174,8 @@ config DEBUG_SHIRQ config LOCKUP_DETECTOR bool "Detect Hard and Soft Lockups" depends on DEBUG_KERNEL && !S390 + # Lockup detector currently prevents NO_HZ_FULL from working + depends on !NO_HZ_FULL help Say Y here to enable the kernel to act as a watchdog to detect hard and soft lockups. -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/