1 #ifndef _LTTNG_GETCPU_H
2 #define _LTTNG_GETCPU_H
5 * Copyright (c) 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
22 #include <urcu/compiler.h>
23 #include <urcu/system.h>
24 #include <urcu/arch.h>
27 void lttng_ust_getcpu_init(void);
29 extern int (*lttng_get_cpu
)(void);
31 #ifdef LTTNG_UST_DEBUG_VALGRIND
34 * Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
35 * get_cpu() returns the current CPU number. It may change due to
36 * migration, so it is only statistically accurate.
39 int lttng_ust_get_cpu_internal(void)
51 #if !HAVE_SCHED_GETCPU
52 #include <sys/syscall.h>
53 #define __getcpu(cpu, node, cache) syscall(__NR_getcpu, cpu, node, cache)
55 * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
58 int lttng_ust_get_cpu_internal(void)
62 ret
= __getcpu(&cpu
, NULL
, NULL
);
63 if (caa_unlikely(ret
< 0))
67 #else /* HAVE_SCHED_GETCPU */
71 * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
74 int lttng_ust_get_cpu_internal(void)
79 if (caa_unlikely(cpu
< 0))
83 #endif /* HAVE_SCHED_GETCPU */
85 #elif (defined(__FreeBSD__) || defined(__CYGWIN__))
88 * FreeBSD and Cygwin do not allow query of CPU ID. Always use CPU
89 * number 0, with the assocated performance degradation on SMP.
92 int lttng_ust_get_cpu_internal(void)
98 #error "Please add support for your OS into liblttng-ust/compat.h."
104 int lttng_ust_get_cpu(void)
106 int (*getcpu
)(void) = CMM_LOAD_SHARED(lttng_get_cpu
);
108 if (caa_likely(!getcpu
)) {
109 return lttng_ust_get_cpu_internal();
115 #endif /* _LTTNG_GETCPU_H */
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