From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755337Ab3EJVSb (ORCPT ); Fri, 10 May 2013 17:18:31 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:13174 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754640Ab3EJVS1 (ORCPT ); Fri, 10 May 2013 17:18:27 -0400 X-Authority-Analysis: v=2.0 cv=UO1f7Vjy c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=Ciwy3NGCPMMA:10 a=jB67A_zoR28A:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=0cHSfWUJHcEA:10 a=NpxI-HVzja7l_C84ficA:9 a=jeBq3FmKZ4MA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-Id: <20130510211825.655823570@goodmis.org> User-Agent: quilt/0.60-1 Date: Fri, 10 May 2013 17:12:28 -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 3/3] nohz: Warn if the machine can not perform nohz_full References: <20130510211225.594959788@goodmis.org> Content-Disposition: inline; filename=warn-no-hz.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If the user configures NO_HZ_FULL and defines nohz_full=XXX on the kerenl command line, or enables NO_HZ_FULL_ALL, but nohz fails due to the machine having a unstable clock, warn about it. We do not want users thinking that they are getting the benefit of nohz when their machine can not support it. Signed-off-by: Steven Rostedt Index: linux-trace.git/kernel/time/tick-sched.c =================================================================== --- linux-trace.git.orig/kernel/time/tick-sched.c +++ linux-trace.git/kernel/time/tick-sched.c @@ -178,6 +178,11 @@ static bool can_stop_full_tick(void) */ if (!sched_clock_stable) { trace_tick_stop(0, "unstable sched clock\n"); + /* + * Don't allow the user to think they can get + * full NO_HZ with this machine. + */ + WARN_ONCE(1, "NO_HZ FULL will not work with unstable sched clock"); return false; } #endif