hwlat-detector: Use trace_clock_local if available

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().

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

diff --git a/drivers/misc/hwlat_detector.c b/drivers/misc/hwlat_detector.c
index c07e85932cbf7d6ffa04533bdd871bdd5431cea0..0fcc0e38df42723149e02da32fcd6aab945f09ac 100644 (file)
--- 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 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) {
                                pr_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) {