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 #define _GNU_SOURCE
  23 #include <urcu/compiler.h>
  24 #include <sched.h>
  25
  26 #ifdef UST_VALGRIND
  27
  28 /*
  29  * Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
  30  * get_cpu() returns the current CPU number. It may change due to
  31  * migration, so it is only statistically accurate.
  32  */
  33 static inline
  34 int lttng_ust_get_cpu(void)
  35 {
  36         return 0;
  37 }
  38
  39 #else
  40
  41 /*
  42  * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
  43  */
  44 static inline
  45 int lttng_ust_get_cpu(void)
  46 {
  47         int cpu;
  48
  49         cpu = sched_getcpu();
  50         if (caa_unlikely(cpu < 0))
  51                 return 0;
  52         return cpu;
  53 }
  54
  55 #endif
  56
  57 #endif /* _LTTNG_GETCPU_H */