wrapper/trace-clock.h

   1 #ifndef _LTTNG_TRACE_CLOCK_H
   2 #define _LTTNG_TRACE_CLOCK_H
   3
   4 /*
   5  * wrapper/trace-clock.h
   6  *
   7  * Contains LTTng trace clock mapping to LTTng trace clock or mainline monotonic
   8  * clock. This wrapper depends on CONFIG_HIGH_RES_TIMERS=y.
   9  *
  10  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  11  *
  12  * This library is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU Lesser General Public
  14  * License as published by the Free Software Foundation; only
  15  * version 2.1 of the License.
  16  *
  17  * This library is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  20  * Lesser General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public
  23  * License along with this library; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  25  */
  26
  27 #ifdef CONFIG_HAVE_TRACE_CLOCK
  28 #include <linux/trace-clock.h>
  29 #else /* CONFIG_HAVE_TRACE_CLOCK */
  30
  31 #include <linux/hardirq.h>
  32 #include <linux/ktime.h>
  33 #include <linux/time.h>
  34 #include <linux/hrtimer.h>
  35 #include <linux/version.h>
  36 #include "random.h"
  37
  38 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,10,0))
  39 #error "Linux kernels 3.10 and 3.11 introduce a deadlock in the timekeeping subsystem. See http://lkml.kernel.org/r/1378943457-27314-1-git-send-email-john.stultz@linaro.org for details. Awaiting patch merge into Linux master, stable-3.10 and stable-3.11 for fine-grained kernel version blacklisting."
  40 #endif
  41
  42 static inline u64 trace_clock_monotonic_wrapper(void)
  43 {
  44         ktime_t ktime;
  45
  46         /*
  47          * Refuse to trace from NMIs with this wrapper, because an NMI could
  48          * nest over the xtime write seqlock and deadlock.
  49          */
  50         if (in_nmi())
  51                 return (u64) -EIO;
  52
  53         ktime = ktime_get();
  54         return ktime_to_ns(ktime);
  55 }
  56
  57 static inline u32 trace_clock_read32(void)
  58 {
  59         return (u32) trace_clock_monotonic_wrapper();
  60 }
  61
  62 static inline u64 trace_clock_read64(void)
  63 {
  64         return (u64) trace_clock_monotonic_wrapper();
  65 }
  66
  67 static inline u64 trace_clock_freq(void)
  68 {
  69         return (u64) NSEC_PER_SEC;
  70 }
  71
  72 static inline int trace_clock_uuid(char *uuid)
  73 {
  74         return wrapper_get_bootid(uuid);
  75 }
  76
  77 static inline int get_trace_clock(void)
  78 {
  79         /*
  80          * LTTng: Using mainline kernel monotonic clock. NMIs will not be
  81          * traced, and expect significant performance degradation compared to
  82          * the LTTng trace clocks. Integration of the LTTng 0.x trace clocks
  83          * into LTTng 2.0 is planned in a near future.
  84          */
  85         printk(KERN_WARNING "LTTng: Using mainline kernel monotonic clock.\n");
  86         printk(KERN_WARNING "  * NMIs will not be traced,\n");
  87         printk(KERN_WARNING "  * expect significant performance degradation compared to the\n");
  88         printk(KERN_WARNING "    LTTng trace clocks.\n");
  89         printk(KERN_WARNING "Integration of the LTTng 0.x trace clocks into LTTng 2.0 is planned\n");
  90         printk(KERN_WARNING "in a near future.\n");
  91
  92         return 0;
  93 }
  94
  95 static inline void put_trace_clock(void)
  96 {
  97 }
  98
  99 #endif /* CONFIG_HAVE_TRACE_CLOCK */
 100
 101 #endif /* _LTTNG_TRACE_CLOCK_H */