From 60303ed3f4b9332b9aa9bc17c68bc174e7343e2d Mon Sep 17 00:00:00 2001 From: David Sharp <dhsharp@google.com> Date: Thu, 11 Oct 2012 16:27:52 -0700 Subject: [PATCH] tracing: Reset ring buffer when changing trace_clocks 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/1349998076-15495-3-git-send-email-dhsharp@google.com Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: David Sharp <dhsharp@google.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- kernel/trace/trace.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 88111b08b2c1d..6ed6013dff2b4 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; -- GitLab