From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752816AbeDFNFM (ORCPT ); Fri, 6 Apr 2018 09:05:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:59832 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752604AbeDFNBN (ORCPT ); Fri, 6 Apr 2018 09:01:13 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3258521837 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Message-Id: <20180406130112.118951478@goodmis.org> User-Agent: quilt/0.63-1 Date: Fri, 06 Apr 2018 09:00:38 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Chris Wilson Subject: [for-next][PATCH 03/18] tracing: Default to using trace_global_clock if sched_clock is unstable References: <20180406130035.400292196@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=0003-tracing-Default-to-using-trace_global_clock-if-sched.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Chris Wilson Across suspend, we may see a very large drift in timestamps if the sched clock is unstable, prompting the global trace's ringbuffer code to warn and suggest switching to the global clock. Preempt this request by detecting when the sched clock is unstable (determined during late_initcall) and automatically switching the default clock over to trace_global_clock. This should prevent requiring user interaction to resolve warnings such as: Delta way too big! 18446743856563626466 ts=18446744054496180323 write stamp = 197932553857 If you just came from a suspend/resume, please switch to the trace global clock: echo global > /sys/kernel/debug/tracing/trace_clock Link: http://lkml.kernel.org/r/20180330150132.16903-1-chris@chris-wilson.co.uk Signed-off-by: Chris Wilson Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 551a7cd0d705..0f47e653ffd8 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -41,6 +41,7 @@ #include #include #include +#include #include #include "trace.h" @@ -8596,3 +8597,21 @@ __init static int clear_boot_tracer(void) fs_initcall(tracer_init_tracefs); late_initcall_sync(clear_boot_tracer); + +#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK +__init static int tracing_set_default_clock(void) +{ + /* sched_clock_stable() is determined in late_initcall */ + if (trace_boot_clock || sched_clock_stable()) { + printk(KERN_WARNING + "Unstable clock detected, switching default tracing clock to \"global\"\n" + "If you want to keep using the local clock, then add:\n" + " \"trace_clock=local\"\n" + "on the kernel command line\n"); + tracing_set_clock(&global_trace, "global"); + } + + return 0; +} +late_initcall_sync(tracing_set_default_clock); +#endif -- 2.15.1