From: David Sharp <[email protected]> Because the "tsc" clock isn't in nanoseconds, the ring buffer must be reset when changing clocks so that incomparable timestamps don't end up in the same trace.
Tested: Confirmed switching clocks resets the trace buffer. Google-Bug-Id: 6980623 Link: http://lkml.kernel.org/r/[email protected] Cc: Masami Hiramatsu <[email protected]> Signed-off-by: David Sharp <[email protected]> Signed-off-by: Steven Rostedt <[email protected]> --- kernel/trace/trace.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 88111b0..6ed6013 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4073,6 +4073,14 @@ static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf, if (max_tr.buffer) ring_buffer_set_clock(max_tr.buffer, trace_clocks[i].func); + /* + * New clock may not be consistent with the previous clock. + * Reset the buffer so that it doesn't have incomparable timestamps. + */ + tracing_reset_online_cpus(&global_trace); + if (max_tr.buffer) + tracing_reset_online_cpus(&max_tr); + mutex_unlock(&trace_types_lock); *fpos += cnt; -- 1.7.10.4
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