linux-kernel - [PATCH v2 3/3] trace-cmd: setting plugin to 'nop' clears data before it's recorded

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Message-ID: <1333899525-6436-1-git-send-email-mark.asselstine@windriver.com>
Date:	Sun, 8 Apr 2012 11:38:45 -0400
From:	Mark Asselstine <mark.asselstine@...driver.com>
To:	<rostedt@...dmis.org>
CC:	<linux-kernel@...r.kernel.org>, <asselsm@...il.com>
Subject: [PATCH v2 3/3] trace-cmd: setting plugin to 'nop' clears data before it's recorded

commit e09a5db1a929ab668c273b87c4f0a32b81e1c21a
[trace-cmd: Add trace-cmd record --date option]

moved the call to disable_all() in trace_record() from after record_data()
to before it. Unfortunately disable_all() sets 'nop' in 'current_tracer'
which has the side affect of clearing 'trace', thus all the latency tracer
reports are empty/useless. Here we make disable_all() optionally call
set_plugin() thus, where we need to, we can delay the disabling of the tracer
until we have had a chance to capture 'trace'. We have added this delayed
behavior to trace_record() to fix the latency reports, for all other calls to
disable_all() we continue to have set_plugin() called.

Signed-off-by: Mark Asselstine <mark.asselstine@...driver.com>
---
[v2] * remove redundant conditional usage
     * add conditional param for disable_all() instead of adding new func
     * used int and not gboolean to avoid gtk includes where not needed

 trace-record.c |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/trace-record.c b/trace-record.c
index 1c56fa9..95d4a2a 100644
--- a/trace-record.c
+++ b/trace-record.c
@@ -897,11 +897,13 @@ static void disable_tracing(void)
 	write_tracing_on(0);
 }
 
-static void disable_all(void)
+static void disable_all(int disable_tracer)
 {
 	disable_tracing();
 
-	set_plugin("nop");
+	if (disable_tracer)
+		set_plugin("nop");
+
 	reset_events();
 
 	/* Force close and reset of ftrace pid file */
@@ -1573,7 +1575,7 @@ static void set_funcs(void)
 	/* make sure we are filtering functions */
 	if (func_stack) {
 		if (!functions_filtered()) {
-			disable_all();
+			disable_all(1);
 			die("Function stack trace set, but functions not filtered");
 		}
 		save_option(FUNC_STACK_TRACE);
@@ -1938,7 +1940,7 @@ void trace_record (int argc, char **argv)
 				break;
 			}
 		}
-		disable_all();
+		disable_all(1);
 		set_buffer_size();
 		exit(0);
 	} else
@@ -2147,7 +2149,7 @@ void trace_record (int argc, char **argv)
 
 	if (!extract) {
 		fset = set_ftrace(!disable);
-		disable_all();
+		disable_all(1);
 
 		/* Record records the date first */
 		if (record && date)
@@ -2227,7 +2229,7 @@ void trace_record (int argc, char **argv)
 	}
 
 	if (!keep)
-		disable_all();
+		disable_all(0);
 
 	printf("Kernel buffer statistics:\n"
 	       "  Note: \"entries\" are the entries left in the kernel ring buffer and are not\n"
@@ -2249,6 +2251,8 @@ void trace_record (int argc, char **argv)
 	if (keep)
 		exit(0);
 
+	set_plugin("nop");
+
 	/* If tracing_on was enabled before we started, set it on now */
 	if (tracing_on_init_val)
 		write_tracing_on(tracing_on_init_val);
-- 
1.7.5.4

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