wrapper/trace-clock.h

   1 /*
   2  * Copyright (C) 2011 Mathieu Desnoyers (mathieu.desnoyers@efficios.com)
   3  *
   4  * Contains LTTng trace clock mapping to LTTng trace clock or mainline monotonic
   5  * clock. This wrapper depends on CONFIG_HIGH_RES_TIMERS=y.
   6  *
   7  * Dual LGPL v2.1/GPL v2 license.
   8  */
   9
  10 #ifndef _LTTNG_TRACE_CLOCK_H
  11 #define _LTTNG_TRACE_CLOCK_H
  12
  13 #ifdef CONFIG_HAVE_TRACE_CLOCK
  14 #include <linux/trace-clock.h>
  15 #else /* CONFIG_HAVE_TRACE_CLOCK */
  16
  17 #include <linux/hardirq.h>
  18 #include <linux/ktime.h>
  19 #include <linux/time.h>
  20 #include <linux/hrtimer.h>
  21
  22 static inline u64 trace_clock_monotonic_wrapper(void)
  23 {
  24         ktime_t ktime;
  25
  26         /*
  27          * Refuse to trace from NMIs with this wrapper, because an NMI could
  28          * nest over the xtime write seqlock and deadlock.
  29          */
  30         if (in_nmi())
  31                 return (u64) -EIO;
  32
  33         ktime = ktime_get();
  34         return (u64) ktime.tv64;
  35 }
  36
  37 static inline u32 trace_clock_read32(void)
  38 {
  39         return (u32) trace_clock_monotonic_wrapper();
  40 }
  41
  42 static inline u64 trace_clock_read64(void)
  43 {
  44         return (u64) trace_clock_monotonic_wrapper();
  45 }
  46
  47 static inline u64 trace_clock_freq(void)
  48 {
  49         return (u64) NSEC_PER_SEC;
  50 }
  51
  52 static inline const char *trace_clock_uuid(void)
  53 {
  54         return "CLOCK_MONOTONIC";
  55 }
  56
  57 static inline int get_trace_clock(void)
  58 {
  59         /*
  60          * LTTng: Using mainline kernel monotonic clock. NMIs will not be
  61          * traced, and expect significant performance degradation compared to
  62          * the LTTng trace clocks. Integration of the LTTng 0.x trace clocks
  63          * into LTTng 2.0 is planned in a near future.
  64          */
  65         printk(KERN_WARNING "LTTng: Using mainline kernel monotonic clock.\n");
  66         printk(KERN_WARNING "  * NMIs will not be traced,\n");
  67         printk(KERN_WARNING "  * expect significant performance degradation compared to the\n");
  68         printk(KERN_WARNING "    LTTng trace clocks.\n");
  69         printk(KERN_WARNING "Integration of the LTTng 0.x trace clocks into LTTng 2.0 is planned\n");
  70         printk(KERN_WARNING "in a near future.\n");
  71
  72         return 0;
  73 }
  74
  75 static inline void put_trace_clock(void)
  76 {
  77 }
  78
  79 #endif /* CONFIG_HAVE_TRACE_CLOCK */
  80
  81 #endif /* _LTTNG_TRACE_CLOCK_H */