From: Steven Rostedt <rost...@goodmis.org>
As ktime_get() calls into the timing code which does a read_seq(), it
may be affected by other CPUS that touch that lock. To remove this
dependency, use the trace_clock_local() which is already exported
for module use. If CONFIG_TRACING is enabled, use that as the clock,
otherwise use ktime_get().
Cc: stable...@vger.kernel.org
Signed-off-by: Steven Rostedt <srost...@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
---
drivers/misc/hwlat_detector.c | 34 +++++++++++++++++++++++++---------
1 file changed, 25 insertions(+), 9 deletions(-)
diff --git a/drivers/misc/hwlat_detector.c b/drivers/misc/hwlat_detector.c
index f93b8ef..13443e9 100644
--- a/drivers/misc/hwlat_detector.c
+++ b/drivers/misc/hwlat_detector.c
@@ -51,6 +51,7 @@
#include <linux/version.h>
#include <linux/delay.h>
#include <linux/slab.h>
+#include <linux/trace_clock.h>
#define BUF_SIZE_DEFAULT 262144UL /* 8K*(sizeof(entry)) */
#define BUF_FLAGS (RB_FL_OVERWRITE) /* no block on full */
@@ -211,6 +212,21 @@ static struct sample *buffer_get_sample(struct sample
*sample)
return sample;
}
+#ifndef CONFIG_TRACING
+#define time_type ktime_t
+#define time_get() ktime_get()
+#define time_to_us(x) ktime_to_us(x)
+#define time_sub(a, b) ktime_sub(a, b)
+#define init_time(a, b) (a).tv64 = b
+#define time_u64(a) (a).tv64
+#else
+#define time_type u64
+#define time_get() trace_clock_local()
+#define time_to_us(x) div_u64(x, 1000)
+#define time_sub(a, b) ((a) - (b))
+#define init_time(a, b) a = b
+#define time_u64(a) a
+#endif
/**
* get_sample - sample the CPU TSC and look for likely hardware latencies
* @unused: This is not used but is a part of the stop_machine API
@@ -220,23 +236,23 @@ static struct sample *buffer_get_sample(struct sample
*sample)
*/
static int get_sample(void *unused)
{
- ktime_t start, t1, t2, last_t2;
+ time_type start, t1, t2, last_t2;
s64 diff, total = 0;
u64 sample = 0;
u64 outer_sample = 0;
int ret = 1;
- last_t2.tv64 = 0;
- start = ktime_get(); /* start timestamp */
+ init_time(last_t2, 0);
+ start = time_get(); /* start timestamp */
do {
- t1 = ktime_get(); /* we'll look for a discontinuity */
- t2 = ktime_get();
+ t1 = time_get(); /* we'll look for a discontinuity */
+ t2 = time_get();
- if (last_t2.tv64) {
+ if (time_u64(last_t2)) {
/* Check the delta from the outer loop (t2 to next t1)
*/
- diff = ktime_to_us(ktime_sub(t1, last_t2));
+ diff = time_to_us(time_sub(t1, last_t2));
/* This shouldn't happen */
if (diff < 0) {
printk(KERN_ERR BANNER "time running
backwards\n");
@@ -247,10 +263,10 @@ static int get_sample(void *unused)
}
last_t2 = t2;
- total = ktime_to_us(ktime_sub(t2, start)); /* sample width */
+ total = time_to_us(time_sub(t2, start)); /* sample width */
/* This checks the inner loop (t1 to t2) */
- diff = ktime_to_us(ktime_sub(t2, t1)); /* current diff */
+ diff = time_to_us(time_sub(t2, t1)); /* current diff */
/* This shouldn't happen */
if (diff < 0) {
--
1.7.10.4
--
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