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From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@elte.hu>,
	Andrew Morton <akpm@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Lai Jiangshan <laijs@cn.fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	Steven Rostedt <srostedt@redhat.com>
Subject: [PATCH 01/16] tracing: fix comments about trace buffer resizing
Date: Thu, 12 Mar 2009 22:37:05 -0400	[thread overview]
Message-ID: <20090313023825.008224270@goodmis.org> (raw)
In-Reply-To: 20090313023704.971438367@goodmis.org

[-- Attachment #1: 0001-tracing-fix-comments-about-trace-buffer-resizing.patch --]
[-- Type: text/plain, Size: 1778 bytes --]

From: Steven Rostedt <srostedt@redhat.com>

Impact: cleanup

Some of the comments about the trace buffer resizing is gobbledygook.
And I wonder why people question if I'm a native English speaker.

This patch makes the comments make a bit more sense.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 kernel/trace/trace.c |   19 ++++++++++++++++---
 1 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c3946a6..c61ee85 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2336,7 +2336,8 @@ static int tracing_resize_ring_buffer(unsigned long size)
 
 	/*
 	 * If kernel or user changes the size of the ring buffer
-	 * it get completed.
+	 * we use the size that was given, and we can forget about
+	 * expanding it later.
 	 */
 	ring_buffer_expanded = 1;
 
@@ -2351,8 +2352,20 @@ static int tracing_resize_ring_buffer(unsigned long size)
 		r = ring_buffer_resize(global_trace.buffer,
 				       global_trace.entries);
 		if (r < 0) {
-			/* AARGH! We are left with different
-			 * size max buffer!!!! */
+			/*
+			 * AARGH! We are left with different
+			 * size max buffer!!!!
+			 * The max buffer is our "snapshot" buffer.
+			 * When a tracer needs a snapshot (one of the
+			 * latency tracers), it swaps the max buffer
+			 * with the saved snap shot. We succeeded to
+			 * update the size of the main buffer, but failed to
+			 * update the size of the max buffer. But when we tried
+			 * to reset the main buffer to the original size, we
+			 * failed there too. This is very unlikely to
+			 * happen, but if it does, warn and kill all
+			 * tracing.
+			 */
 			WARN_ON(1);
 			tracing_disabled = 1;
 		}
-- 
1.6.1.3

-- 

  reply	other threads:[~2009-03-13  2:39 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-03-13  2:37 [PATCH 00/16] [GIT PULL] updates for tip/tracing/ftrace Steven Rostedt
2009-03-13  2:37 ` Steven Rostedt [this message]
2009-03-13  2:37 ` [PATCH 02/16] tracing: protect ring_buffer_expanded with trace_types_lock Steven Rostedt
2009-03-13  2:37 ` [PATCH 03/16] ring-buffer: use CONFIG_HOTPLUG_CPU not CONFIG_HOTPLUG Steven Rostedt
2009-03-13  2:37 ` [PATCH 04/16] ring-buffer: remove unneeded get_online_cpus Steven Rostedt
2009-03-13  2:37 ` [PATCH 05/16] tracing: show that buffer size is not expanded Steven Rostedt
2009-03-13  3:05   ` KOSAKI Motohiro
2009-03-13  3:20     ` Steven Rostedt
2009-03-13  3:28       ` KOSAKI Motohiro
2009-03-13  2:37 ` [PATCH 06/16] tracing/core: bring back raw trace_printk for dynamic formats strings Steven Rostedt
2009-03-13  2:37 ` [PATCH 07/16] tracing: make bprint event use the proper event id Steven Rostedt
2009-03-13  2:37 ` [PATCH 08/16] tracing: have event_trace_printk use static tracer Steven Rostedt
2009-03-13  2:49   ` Andrew Morton
2009-03-13  3:08     ` Steven Rostedt
2009-03-13  3:09   ` KOSAKI Motohiro
2009-03-13  3:17     ` Steven Rostedt
2009-03-13  3:28       ` KOSAKI Motohiro
2009-03-13  3:34         ` Steven Rostedt
2009-03-13  5:36         ` [tip:tracing/ftrace] tracing: add comment for use of double __builtin_consant_p Steven Rostedt
2009-03-13  2:37 ` [PATCH 09/16] tracing: export trace formats to user space Steven Rostedt
2009-03-13 15:03   ` Frederic Weisbecker
2009-03-13  2:37 ` [PATCH 10/16] tracing: fix stack tracer header Steven Rostedt
2009-03-13  2:37 ` [PATCH 11/16] tracing: explain why stack tracer is empty Steven Rostedt
2009-03-13  2:37 ` [PATCH 12/16] tracing: tracepoints for softirq entry/exit - add softirq-to-name array Steven Rostedt
2009-03-13  4:12   ` Andrew Morton
2009-03-13  4:22     ` Steven Rostedt
2009-03-13  2:37 ` [PATCH 13/16] tracing: tracepoints for softirq entry/exit - tracepoints Steven Rostedt
2009-03-13  2:37 ` [PATCH 14/16] tracing: Dont use tracing_record_cmdline() in workqueue tracer fix Steven Rostedt
2009-03-13  2:37 ` [PATCH 15/16] tracing: show event name in trace for TRACE_EVENT created events Steven Rostedt
2009-03-13  2:37 ` [PATCH 16/16] ring-buffer: document reader page design Steven Rostedt
2009-03-13  3:35 ` [PATCH 00/16] [GIT PULL] updates for tip/tracing/ftrace Ingo Molnar

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