libringbuffer/getcpu.h

   1 #ifndef _LTTNG_GETCPU_H
   2 #define _LTTNG_GETCPU_H
   3
   4 /*
   5  * Copyright (c) 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; only
  10  * version 2.1 of the License.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with this library; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include <urcu/compiler.h>
  23
  24 #ifdef UST_VALGRIND
  25
  26 /*
  27  * Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
  28  * get_cpu() returns the current CPU number. It may change due to
  29  * migration, so it is only statistically accurate.
  30  */
  31 static inline
  32 int lttng_ust_get_cpu(void)
  33 {
  34         return 0;
  35 }
  36
  37 #else
  38
  39 /*
  40  * sched_getcpu.
  41  */
  42 #ifdef __linux__
  43
  44 #ifdef __UCLIBC__
  45 #include <sys/syscall.h>
  46 #define __getcpu(cpu, node, cache)      syscall(__NR_getcpu, cpu, node, cache)
  47 /*
  48  * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
  49  */
  50 static inline
  51 int lttng_ust_get_cpu(void)
  52 {
  53         int cpu, ret;
  54
  55         ret = __getcpu(&cpu, NULL, NULL);
  56         if (caa_unlikely(ret < 0))
  57                 return 0;
  58         return c;
  59 }
  60 #else /* __UCLIBC__ */
  61 #include <sched.h>
  62
  63 /*
  64  * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
  65  */
  66 static inline
  67 int lttng_ust_get_cpu(void)
  68 {
  69         int cpu;
  70
  71         cpu = sched_getcpu();
  72         if (caa_unlikely(cpu < 0))
  73                 return 0;
  74         return cpu;
  75 }
  76 #endif  /* __UCLIBC__ */
  77
  78 #elif defined(__FreeBSD__)
  79
  80 /*
  81  * FreeBSD does not allow query of CPU ID. Always use CPU number 0, with
  82  * the assocated performance degradation on SMP.
  83  */
  84 static inline
  85 int lttng_ust_get_cpu(void)
  86 {
  87         return 0;
  88 }
  89
  90 #else
  91 #error "Please add support for your OS into liblttng-ust/compat.h."
  92 #endif
  93
  94 #endif
  95
  96 #endif /* _LTTNG_GETCPU_H */