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 "../lttng-kernel-version.h"
  37 #include "random.h"
  38
  39 #if LTTNG_KERNEL_RANGE(3,10,0, 3,10,14) || LTTNG_KERNEL_RANGE(3,11,0, 3,11,3)
  40 #error "Linux kernels 3.10 and 3.11 introduce a deadlock in the timekeeping subsystem. Fixed by commit 7bd36014460f793c19e7d6c94dab67b0afcfcb7f \"timekeeping: Fix HRTICK related deadlock from ntp lock changes\" in Linux."
  41 #endif
  42
  43 static inline u64 trace_clock_monotonic_wrapper(void)
  44 {
  45         ktime_t ktime;
  46
  47         /*
  48          * Refuse to trace from NMIs with this wrapper, because an NMI could
  49          * nest over the xtime write seqlock and deadlock.
  50          */
  51         if (in_nmi())
  52                 return (u64) -EIO;
  53
  54         ktime = ktime_get();
  55         return ktime_to_ns(ktime);
  56 }
  57
  58 static inline u32 trace_clock_read32(void)
  59 {
  60         return (u32) trace_clock_monotonic_wrapper();
  61 }
  62
  63 static inline u64 trace_clock_read64(void)
  64 {
  65         return (u64) trace_clock_monotonic_wrapper();
  66 }
  67
  68 static inline u64 trace_clock_freq(void)
  69 {
  70         return (u64) NSEC_PER_SEC;
  71 }
  72
  73 static inline int trace_clock_uuid(char *uuid)
  74 {
  75         return wrapper_get_bootid(uuid);
  76 }
  77
  78 static inline int get_trace_clock(void)
  79 {
  80         /*
  81          * LTTng: Using mainline kernel monotonic clock. NMIs will not be
  82          * traced, and expect significant performance degradation compared to
  83          * the LTTng trace clocks. Integration of the LTTng 0.x trace clocks
  84          * into LTTng 2.0 is planned in a near future.
  85          */
  86         printk(KERN_WARNING "LTTng: Using mainline kernel monotonic clock.\n");
  87         printk(KERN_WARNING "  * NMIs will not be traced,\n");
  88         printk(KERN_WARNING "  * expect significant performance degradation compared to the\n");
  89         printk(KERN_WARNING "    LTTng trace clocks.\n");
  90         printk(KERN_WARNING "Integration of the LTTng 0.x trace clocks into LTTng 2.0 is planned\n");
  91         printk(KERN_WARNING "in a near future.\n");
  92
  93         return 0;
  94 }
  95
  96 static inline void put_trace_clock(void)
  97 {
  98 }
  99
 100 #endif /* CONFIG_HAVE_TRACE_CLOCK */
 101
 102 #endif /* _LTTNG_TRACE_CLOCK_H */