From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755138Ab3EJVS3 (ORCPT ); Fri, 10 May 2013 17:18:29 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:28393 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754404Ab3EJVS0 (ORCPT ); Fri, 10 May 2013 17:18:26 -0400 X-Authority-Analysis: v=2.0 cv=L+efspv8 c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=Ciwy3NGCPMMA:10 a=lCtUp-edVtwA:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=ASeoVxjNus4A:10 a=fftbd8lyitm2-44GTeUA:9 a=jeBq3FmKZ4MA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-Id: <20130510211825.504050840@goodmis.org> User-Agent: quilt/0.60-1 Date: Fri, 10 May 2013 17:12:27 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Frederic Weisbecker , "Paul E. McKenney" , Ingo Molnar , Andrew Morton , Thomas Gleixner , "H. Peter Anvin" Subject: [PATCH 2/3] nohz: Disable LOCKUP_DETECTOR when NO_HZ_FULL is enabled References: <20130510211225.594959788@goodmis.org> Content-Disposition: inline; filename=no-hz-full-prevents-lockup-detector.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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.