From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759689Ab2ILCsA (ORCPT ); Tue, 11 Sep 2012 22:48:00 -0400 Received: from mail-lb0-f202.google.com ([209.85.217.202]:59907 "EHLO mail-lb0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758186Ab2ILCr7 (ORCPT ); Tue, 11 Sep 2012 22:47:59 -0400 From: David Sharp To: linux-kernel@vger.kernel.org Cc: David Sharp , Steven Rostedt , Masami Hiramatsu Subject: [PATCH 2/3] tracing: reset ring buffer when changing trace_clocks Date: Tue, 11 Sep 2012 19:41:10 -0700 Message-Id: <1347417671-22998-3-git-send-email-dhsharp@google.com> X-Mailer: git-send-email 1.7.7.3 In-Reply-To: <1347417671-22998-1-git-send-email-dhsharp@google.com> References: <1347417671-22998-1-git-send-email-dhsharp@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: David Sharp --- kernel/trace/trace.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index dc1f1fa..6911f35 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4014,6 +4014,14 @@ 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; -- 1.7.7.3