From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753342Ab1CJQAE (ORCPT ); Thu, 10 Mar 2011 11:00:04 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.125]:41186 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752573Ab1CJP7O (ORCPT ); Thu, 10 Mar 2011 10:59:14 -0500 X-Authority-Analysis: v=1.1 cv=UQuFHoD2CPQ248x8AXEbKhr4z9AaDqApxmEl3BhfZ64= c=1 sm=0 a=wZezGcEurugA:10 a=bbbx4UPp9XUA:10 a=OPBmh+XkhLl+Enan7BmTLg==:17 a=20KFwNOVAAAA:8 a=meVymXHHAAAA:8 a=JIAjFgqsX2v0nRl9AKkA:9 a=cfCPEVovJ5Dxy63spN7ydoWom4gA:4 a=jEp0ucaQiEUA:10 a=jeBq3FmKZ4MA:10 a=OPBmh+XkhLl+Enan7BmTLg==:117 X-Cloudmark-Score: 0 X-Originating-IP: 67.242.120.143 Message-Id: <20110310155912.029198359@goodmis.org> User-Agent: quilt/0.48-1 Date: Thu, 10 Mar 2011 10:58:12 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Frederic Weisbecker , Jiri Olsa Subject: [PATCH 12/15] tracing: Explain about unstable clock on resume with ring buffer warning References: <20110310155800.478792851@goodmis.org> Content-Disposition: inline; filename=0012-tracing-Explain-about-unstable-clock-on-resume-with-.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jiri Olsa The "Delta way too big" warning might appear on a system with a unstable shed clock right after the system is resumed and tracing was enabled at time of suspend. Since it's not realy a bug, and the unstable sched clock is working fast and reliable otherwise, Steven suggested to keep using the sched clock in any case and just to make note in the warning itself. v2 changes: - added #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK Signed-off-by: Jiri Olsa LKML-Reference: <20110218145219.GD2604@jolsa.brq.redhat.com> Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 12 ++++++++++-- 1 files changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 3237d96..db7b439 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2172,11 +2172,19 @@ rb_reserve_next_event(struct ring_buffer *buffer, if (likely(ts >= cpu_buffer->write_stamp)) { delta = diff; if (unlikely(test_time_stamp(delta))) { + int local_clock_stable = 1; +#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK + local_clock_stable = sched_clock_stable; +#endif WARN_ONCE(delta > (1ULL << 59), - KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n", + KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s", (unsigned long long)delta, (unsigned long long)ts, - (unsigned long long)cpu_buffer->write_stamp); + (unsigned long long)cpu_buffer->write_stamp, + local_clock_stable ? "" : + "If you just came from a suspend/resume,\n" + "please switch to the trace global clock:\n" + " echo global > /sys/kernel/debug/tracing/trace_clock\n"); add_timestamp = 1; } } -- 1.7.2.3