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 LTTNG_UST_DEBUG_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 /* old uClibc versions didn't have sched_getcpu */
  45 #if defined(__UCLIBC__) && __UCLIBC_MAJOR__ == 0 && \
  46         (__UCLIBC_MINOR__ < 9 || \
  47          (__UCLIBC_MINOR__ == 9 && __UCLIBC_SUBLEVEL__ <= 32))
  48 #include <sys/syscall.h>
  49 #define __getcpu(cpu, node, cache)      syscall(__NR_getcpu, cpu, node, cache)
  50 /*
  51  * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
  52  */
  53 static inline
  54 int lttng_ust_get_cpu(void)
  55 {
  56         int cpu, ret;
  57
  58         ret = __getcpu(&cpu, NULL, NULL);
  59         if (caa_unlikely(ret < 0))
  60                 return 0;
  61         return c;
  62 }
  63 #else /* __UCLIBC__ */
  64 #include <sched.h>
  65
  66 /*
  67  * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
  68  */
  69 static inline
  70 int lttng_ust_get_cpu(void)
  71 {
  72         int cpu;
  73
  74         cpu = sched_getcpu();
  75         if (caa_unlikely(cpu < 0))
  76                 return 0;
  77         return cpu;
  78 }
  79 #endif  /* __UCLIBC__ */
  80
  81 #elif (defined(__FreeBSD__) || defined(__CYGWIN__))
  82
  83 /*
  84  * FreeBSD and Cygwin do not allow query of CPU ID. Always use CPU
  85  * number 0, with the assocated performance degradation on SMP.
  86  */
  87 static inline
  88 int lttng_ust_get_cpu(void)
  89 {
  90         return 0;
  91 }
  92
  93 #else
  94 #error "Please add support for your OS into liblttng-ust/compat.h."
  95 #endif
  96
  97 #endif
  98
  99 #endif /* _LTTNG_GETCPU_H */