libringbuffer/smp.h

   1 #ifndef _LIBRINGBUFFER_SMP_H
   2 #define _LIBRINGBUFFER_SMP_H
   3
   4 /*
   5  * libringbuffer/smp.h
   6  *
   7  * Copyright 2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Dual LGPL v2.1/GPL v2 license.
  10  */
  11
  12 #include <lttng/core.h>
  13
  14 /*
  15  * 4kB of per-cpu data available. Enough to hold the control structures,
  16  * but not ring buffers.
  17  */
  18 #define PER_CPU_MEM_SIZE        4096
  19
  20 extern int __num_possible_cpus;
  21 extern void _get_num_possible_cpus(void);
  22
  23 static inline
  24 int num_possible_cpus(void)
  25 {
  26         if (!__num_possible_cpus)
  27                 _get_num_possible_cpus();
  28         return __num_possible_cpus;
  29 }
  30
  31 /*
  32  * get_cpu() returns the current CPU number. It may change due to
  33  * migration, so it is only statistically accurate.
  34  */
  35 #ifndef UST_VALGRIND
  36 static inline
  37 int get_cpu(void)
  38 {
  39         int cpu;
  40
  41         cpu = sched_getcpu();
  42         if (caa_likely(cpu >= 0))
  43                 return cpu;
  44         /*
  45          * If getcpu(2) is not implemented in the Kernel use CPU 0 as fallback.
  46          */
  47         return 0;
  48 }
  49
  50 #else   /* #else #ifndef UST_VALGRIND */
  51 static inline
  52 int get_cpu(void)
  53 {
  54         /*
  55          * Valgrind does not support the sched_getcpu() vsyscall.
  56          * It causes it to detect a segfault in the program and stop it.
  57          * So if we want to check libust with valgrind, we have to refrain
  58          * from using this call. TODO: it would probably be better to return
  59          * other values too, to better test it.
  60          */
  61         return 0;
  62 }
  63 #endif  /* #else #ifndef UST_VALGRIND */
  64
  65 static inline
  66 void put_cpu(void)
  67 {
  68 }
  69
  70 #define for_each_possible_cpu(cpu)              \
  71         for ((cpu) = 0; (cpu) < num_possible_cpus(); (cpu)++)
  72
  73 #endif /* _LIBRINGBUFFER_SMP_H */