rt-patches/0026-hwlat-detector-Use-trace_clock_local-if-available.patch

   1 From 5a4e0bc5e940b628a8c7e5146dd3ec1a8ed7c1bf Mon Sep 17 00:00:00 2001
   2 From: Steven Rostedt <rostedt@goodmis.org>
   3 Date: Mon, 19 Aug 2013 17:33:26 -0400
   4 Subject: [PATCH 026/366] hwlat-detector: Use trace_clock_local if available
   5
   6 As ktime_get() calls into the timing code which does a read_seq(), it
   7 may be affected by other CPUS that touch that lock. To remove this
   8 dependency, use the trace_clock_local() which is already exported
   9 for module use. If CONFIG_TRACING is enabled, use that as the clock,
  10 otherwise use ktime_get().
  11
  12 Signed-off-by: Steven Rostedt <srostedt@redhat.com>
  13 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  14 ---
  15  drivers/misc/hwlat_detector.c | 34 +++++++++++++++++++++++++---------
  16  1 file changed, 25 insertions(+), 9 deletions(-)
  17
  18 diff --git a/drivers/misc/hwlat_detector.c b/drivers/misc/hwlat_detector.c
  19 index c07e859..0fcc0e3 100644
  20 --- a/drivers/misc/hwlat_detector.c
  21 +++ b/drivers/misc/hwlat_detector.c
  22 @@ -51,6 +51,7 @@
  23  #include <linux/version.h>
  24  #include <linux/delay.h>
  25  #include <linux/slab.h>
  26 +#include <linux/trace_clock.h>
  27
  28  #define BUF_SIZE_DEFAULT       262144UL                /* 8K*(sizeof(entry)) */
  29  #define BUF_FLAGS              (RB_FL_OVERWRITE)       /* no block on full */
  30 @@ -211,6 +212,21 @@ static struct sample *buffer_get_sample(struct sample *sample)
  31         return sample;
  32  }
  33
  34 +#ifndef CONFIG_TRACING
  35 +#define time_type      ktime_t
  36 +#define time_get()     ktime_get()
  37 +#define time_to_us(x)  ktime_to_us(x)
  38 +#define time_sub(a, b) ktime_sub(a, b)
  39 +#define init_time(a, b)        (a).tv64 = b
  40 +#define time_u64(a)    ((a).tv64)
  41 +#else
  42 +#define time_type      u64
  43 +#define time_get()     trace_clock_local()
  44 +#define time_to_us(x)  div_u64(x, 1000)
  45 +#define time_sub(a, b) ((a) - (b))
  46 +#define init_time(a, b)        (a = b)
  47 +#define time_u64(a)    a
  48 +#endif
  49  /**
  50   * get_sample - sample the CPU TSC and look for likely hardware latencies
  51   * @unused: This is not used but is a part of the stop_machine API
  52 @@ -220,23 +236,23 @@ static struct sample *buffer_get_sample(struct sample *sample)
  53   */
  54  static int get_sample(void *unused)
  55  {
  56 -       ktime_t start, t1, t2, last_t2;
  57 +       time_type start, t1, t2, last_t2;
  58         s64 diff, total = 0;
  59         u64 sample = 0;
  60         u64 outer_sample = 0;
  61         int ret = 1;
  62
  63 -       last_t2.tv64 = 0;
  64 -       start = ktime_get(); /* start timestamp */
  65 +       init_time(last_t2, 0);
  66 +       start = time_get(); /* start timestamp */
  67
  68         do {
  69
  70 -               t1 = ktime_get();       /* we'll look for a discontinuity */
  71 -               t2 = ktime_get();
  72 +               t1 = time_get();        /* we'll look for a discontinuity */
  73 +               t2 = time_get();
  74
  75 -               if (last_t2.tv64) {
  76 +               if (time_u64(last_t2)) {
  77                         /* Check the delta from outer loop (t2 to next t1) */
  78 -                       diff = ktime_to_us(ktime_sub(t1, last_t2));
  79 +                       diff = time_to_us(time_sub(t1, last_t2));
  80                         /* This shouldn't happen */
  81                         if (diff < 0) {
  82                                 pr_err(BANNER "time running backwards\n");
  83 @@ -247,10 +263,10 @@ static int get_sample(void *unused)
  84                 }
  85                 last_t2 = t2;
  86
  87 -               total = ktime_to_us(ktime_sub(t2, start)); /* sample width */
  88 +               total = time_to_us(time_sub(t2, start)); /* sample width */
  89
  90                 /* This checks the inner loop (t1 to t2) */
  91 -               diff = ktime_to_us(ktime_sub(t2, t1));     /* current diff */
  92 +               diff = time_to_us(time_sub(t2, t1));     /* current diff */
  93
  94                 /* This shouldn't happen */
  95                 if (diff < 0) {
  96 --
  97 1.9.1
  98