From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752038AbdJCMTO (ORCPT ); Tue, 3 Oct 2017 08:19:14 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59730 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751892AbdJCMTL (ORCPT ); Tue, 3 Oct 2017 08:19:11 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tahsin Erdogan , "Steven Rostedt (VMware)" Subject: [PATCH 3.18 05/24] tracing: Fix trace_pipe behavior for instance traces Date: Tue, 3 Oct 2017 14:18:26 +0200 Message-Id: <20171003113647.349727967@linuxfoundation.org> X-Mailer: git-send-email 2.14.2 In-Reply-To: <20171003113646.772919167@linuxfoundation.org> References: <20171003113646.772919167@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tahsin Erdogan commit 75df6e688ccd517e339a7c422ef7ad73045b18a2 upstream. When reading data from trace_pipe, tracing_wait_pipe() performs a check to see if tracing has been turned off after some data was read. Currently, this check always looks at global trace state, but it should be checking the trace instance where trace_pipe is located at. Because of this bug, cat instances/i1/trace_pipe in the following script will immediately exit instead of waiting for data: cd /sys/kernel/debug/tracing echo 0 > tracing_on mkdir -p instances/i1 echo 1 > instances/i1/tracing_on echo 1 > instances/i1/events/sched/sched_process_exec/enable cat instances/i1/trace_pipe Link: http://lkml.kernel.org/r/20170917102348.1615-1-tahsin@google.com Fixes: 10246fa35d4f ("tracing: give easy way to clear trace buffer") Signed-off-by: Tahsin Erdogan Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4430,7 +4430,7 @@ static int tracing_wait_pipe(struct file * * iter->pos will be 0 if we haven't read anything. */ - if (!tracing_is_on() && iter->pos) + if (!tracer_tracing_is_on(iter->tr) && iter->pos) break; mutex_unlock(&iter->mutex);