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Subject[PATCH] trace: Default to using trace_global_clock if sched_clock is unstable
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

This should prevent requiring user interaction to resolve warnings such

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

Signed-off-by: Chris Wilson <>
Cc: Steven Rostedt (VMware) <>
kernel/trace/trace.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 13baf85b27d8..c5462513db90 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -41,6 +41,7 @@
#include <linux/nmi.h>
#include <linux/fs.h>
#include <linux/trace.h>
+#include <linux/sched/clock.h>
#include <linux/sched/rt.h>

#include "trace.h"
@@ -8505,3 +8506,15 @@ __init static int clear_boot_tracer(void)

+__init static int tracing_set_default_clock(void)
+ /* sched_clock_stable() is determined in late_initcall */
+ if (!trace_boot_clock && !sched_clock_stable())
+ tracing_set_clock(&global_trace, "global");
+ return 0;
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