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From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: [for-next][PATCH 14/21] tracing: Have the document reflect that the trace file keeps tracing enabled
Date: Sun, 29 Mar 2020 14:43:06 -0400	[thread overview]
Message-ID: <20200329184317.504571083@goodmis.org> (raw)
In-Reply-To: 20200329184252.289087453@goodmis.org

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Now that reading the trace file does not temporarly stop tracing while it is
open, update the document to reflect this fact.

Link: http://lkml.kernel.org/r/20200317213417.209675068@goodmis.org

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 Documentation/trace/ftrace.rst | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index c33950a35d65..00621731bf27 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -125,10 +125,13 @@ of ftrace. Here is a list of some of the key files:
   trace:
 
 	This file holds the output of the trace in a human
-	readable format (described below). Note, tracing is temporarily
-	disabled when the file is open for reading. Once all readers
-	are closed, tracing is re-enabled. Opening this file for
+	readable format (described below). Opening this file for
 	writing with the O_TRUNC flag clears the ring buffer content.
+        Note, this file is not a consumer. If tracing is off
+        (no tracer running, or tracing_on is zero), it will produce
+        the same output each time it is read. When tracing is on,
+        it may produce inconsistent results as it tries to read
+        the entire buffer without consuming it.
 
   trace_pipe:
 
@@ -142,9 +145,7 @@ of ftrace. Here is a list of some of the key files:
 	will not be read again with a sequential read. The
 	"trace" file is static, and if the tracer is not
 	adding more data, it will display the same
-	information every time it is read. Unlike the
-	"trace" file, opening this file for reading will not
-	temporarily disable tracing.
+	information every time it is read.
 
   trace_options:
 
-- 
2.25.1



  parent reply	other threads:[~2020-03-29 18:43 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-29 18:42 [for-next][PATCH 00/21] tracing: Updates for v5.7 Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 01/21] tracing: Use address-of operator on section symbols Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 02/21] selftest/ftrace: Fix function trigger test to handle trace not disabling the tracer Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 03/21] tracing: Save off entry when peeking at next entry Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 04/21] ring-buffer: Have ring_buffer_empty() not depend on tracing stopped Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 05/21] ring-buffer: Rename ring_buffer_read() to read_buffer_iter_advance() Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 06/21] ring-buffer: Add page_stamp to iterator for synchronization Steven Rostedt
2020-03-29 18:42 ` [for-next][PATCH 07/21] ring-buffer: Have rb_iter_head_event() handle concurrent writer Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 08/21] ring-buffer: Do not die if rb_iter_peek() fails more than thrice Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 09/21] ring-buffer: Optimize rb_iter_head_event() Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 10/21] ring-buffer: Make resize disable per cpu buffer instead of total buffer Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 11/21] ring-buffer: Do not disable recording when there is an iterator Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 12/21] tracing: Do not disable tracing when reading the trace file Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 13/21] ring-buffer/tracing: Have iterator acknowledge dropped events Steven Rostedt
2020-03-29 18:43 ` Steven Rostedt [this message]
2020-03-29 18:43 ` [for-next][PATCH 15/21] ftrace/kprobe: Show the maxactive number on kprobe_events Steven Rostedt
2020-03-31 13:11   ` Sasha Levin
2020-03-29 18:43 ` [for-next][PATCH 16/21] ftrace: Make function trace pid filtering a bit more exact Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 17/21] ftrace: Create set_ftrace_notrace_pid to not trace tasks Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 18/21] tracing: Create set_event_notrace_pid " Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 19/21] selftests/ftrace: Add test to test new set_ftrace_notrace_pid file Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 20/21] selftests/ftrace: Add test to test new set_event_notrace_pid file Steven Rostedt
2020-03-29 18:43 ` [for-next][PATCH 21/21] tracing: Add documentation on set_ftrace_notrace_pid and set_event_notrace_pid Steven Rostedt

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