linux-kernel - [PATCH v2 2/2] trace: Mention trace_clock=global when warning about unstable clocks

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Message-Id: <20180330150132.16903-2-chris@chris-wilson.co.uk>
Date:   Fri, 30 Mar 2018 16:01:32 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     linux-kernel@...r.kernel.org
Cc:     intel-gfx@...ts.freedesktop.org,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH v2 2/2] trace: Mention trace_clock=global when warning about unstable clocks

Mention the alternative of adding trace_clock=global to the kernel
command line when we detect that we've used an unstable clock across a
suspend/resume cycle.

Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/trace/ring_buffer.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index dcf1c4dd3efe..88098d7fac06 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2637,7 +2637,8 @@ rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
 		  sched_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");
+		  "  echo global > /sys/kernel/debug/tracing/trace_clock\n"
+		  "or add trace_clock=global to the kernel command line\n");
 	info->add_timestamp = 1;
 }
 
-- 
2.16.3