[PATCH 0/2] [GIT PULL] ring-buffer: fixes suggested by Andrew

[PATCH 0/2] [GIT PULL] ring-buffer: fixes suggested by Andrew

[Steven Rostedt]

Ingo,

Please pull the latest tip/tracing/ftrace tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
tip/tracing/ftrace


Steven Rostedt (2):
      ring-buffer: replace constants with time macros in ring-buffer-benchmark
      ring-buffer: check for divide by zero in ring-buffer-benchmark

----
 kernel/trace/ring_buffer_benchmark.c |   18 +++++++++++++-----
 1 files changed, 13 insertions(+), 5 deletions(-)
-- 

[PATCH 1/2] ring-buffer: replace constants with time macros in ring-buffer-benchmark

[Steven Rostedt]

[-- Attachment #1: 0001-ring-buffer-replace-constants-with-time-macros-in-r.patch --]
[-- Type: text/plain, Size: 1805 bytes --]

From: Steven Rostedt <srostedt@redhat.com>

The use of numeric constants is discouraged. It is cleaner and more
descriptive to use macros for constant time conversions.

This patch also removes an extra new line.

[ Impact: more descriptive time conversions ]

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer_benchmark.c |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index a21aa7b..7d3aef9 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -253,7 +253,7 @@ static void ring_buffer_producer(void)
 	}
 
 	time = end_tv.tv_sec - start_tv.tv_sec;
-	time *= 1000000;
+	time *= USEC_PER_SEC;
 	time += (long long)((long)end_tv.tv_usec - (long)start_tv.tv_usec);
 
 	entries = ring_buffer_entries(buffer);
@@ -273,7 +273,8 @@ static void ring_buffer_producer(void)
 	pr_info("Missed:   %ld\n", missed);
 	pr_info("Hit:      %ld\n", hit);
 
-	do_div(time, 1000);
+	/* Convert time from usecs to millisecs */
+	do_div(time, USEC_PER_MSEC);
 	if (time)
 		hit /= (long)time;
 	else
@@ -282,18 +283,19 @@ static void ring_buffer_producer(void)
 	pr_info("Entries per millisec: %ld\n", hit);
 
 	if (hit) {
-		avg = 1000000 / hit;
+		/* Calculate the average time in nanosecs */
+		avg = NSEC_PER_MSEC / hit;
 		pr_info("%ld ns per entry\n", avg);
 	}
 
-
 	if (missed) {
 		if (time)
 			missed /= (long)time;
 
 		pr_info("Total iterations per millisec: %ld\n", hit + missed);
 
-		avg = 1000000 / (hit + missed);
+		/* Caculate the average time in nanosecs */
+		avg = NSEC_PER_MSEC / (hit + missed);
 		pr_info("%ld ns per entry\n", avg);
 	}
 }
-- 
1.6.2.4

-- 

[PATCH 2/2] ring-buffer: check for divide by zero in ring-buffer-benchmark

[Steven Rostedt]

[-- Attachment #1: 0002-ring-buffer-check-for-divide-by-zero-in-ring-buffer.patch --]
[-- Type: text/plain, Size: 1266 bytes --]

From: Steven Rostedt <srostedt@redhat.com>

Although we check if "missed" is not zero, we divide by hit + missed,
and the addition can possible overflow and become a divide by zero.

This patch checks for this case, and will report it when it happens
then modify "hit" to make the calculation be non zero.

[ Impact: prevent possible divide by zero in ring-buffer-benchmark ]

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer_benchmark.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index 7d3aef9..8d68e14 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -294,6 +294,12 @@ static void ring_buffer_producer(void)
 
 		pr_info("Total iterations per millisec: %ld\n", hit + missed);
 
+		/* it is possible that hit + missed will overflow and be zero */
+		if (!(hit + missed)) {
+			pr_info("hit + missed overflowed and totalled zero!\n");
+			hit--; /* make it non zero */
+		}
+
 		/* Caculate the average time in nanosecs */
 		avg = NSEC_PER_MSEC / (hit + missed);
 		pr_info("%ld ns per entry\n", avg);
-- 
1.6.2.4

--