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 _LTT_TRACE_CLOCK_H
  11 #define _LTT_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_frequency(void)
  48 {
  49         return (u64)NSEC_PER_SEC;
  50 }
  51
  52 static inline u32 trace_clock_freq_scale(void)
  53 {
  54         return 1;
  55 }
  56
  57 static inline int get_trace_clock(void)
  58 {
  59         printk(KERN_WARNING "LTTng: Using mainline kernel monotonic clock.\n");
  60         printk(KERN_WARNING "  * NMIs will not be traced,\n");
  61         printk(KERN_WARNING "  * expect significant performance degradation compared to the\n");
  62         printk(KERN_WARNING "    LTTng trace clocks.\n");
  63         printk(KERN_WARNING "You should consider deploying a kernel with the the LTTng kernel\n");
  64         printk(KERN_WARNING "patches, or, better, ask the Linux tracing maintainers to integrate\n");
  65         printk(KERN_WARNING "them if you care deeply about this.\n");
  66
  67 #warning "LTTng: Using mainline kernel monotonic clock. NMIs will not be traced, and expect significant performance degradation compared to the LTTng trace clocks. You should consider deploying a kernel with the the LTTng kernel patches, or, better, ask the Linux tracing maintainers to integrate them if you care deeply about this."
  68
  69         return 0;
  70 }
  71
  72 static inline void put_trace_clock(void)
  73 {
  74 }
  75
  76 #endif /* CONFIG_HAVE_TRACE_CLOCK */
  77
  78 #endif /* _LTT_TRACE_CLOCK_H */