@@ -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)
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())
+ tracing_set_clock(&global_trace, "global");
+
+ return 0;
+}
+late_initcall_sync(tracing_set_default_clock);
+#endif
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 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Steven Rostedt (VMware) <rostedt@goodmis.org> --- kernel/trace/trace.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)