Fix: pass private data to context callbacks
[lttng-ust.git] / libringbuffer / getcpu.h
1 /*
2 * SPDX-License-Identifier: LGPL-2.1-only
3 *
4 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
5 */
6
7 #ifndef _LTTNG_GETCPU_H
8 #define _LTTNG_GETCPU_H
9
10 #include <urcu/compiler.h>
11 #include <urcu/system.h>
12 #include <urcu/arch.h>
13
14 void lttng_ust_getcpu_init(void)
15 __attribute__((visibility("hidden")));
16
17 extern int (*lttng_get_cpu)(void)
18 __attribute__((visibility("hidden")));
19
20 #ifdef LTTNG_UST_DEBUG_VALGRIND
21
22 /*
23 * Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
24 * get_cpu() returns the current CPU number. It may change due to
25 * migration, so it is only statistically accurate.
26 */
27 static inline
28 int lttng_ust_get_cpu_internal(void)
29 {
30 return 0;
31 }
32
33 #else
34
35 /*
36 * sched_getcpu.
37 */
38 #ifdef __linux__
39
40 #if !HAVE_SCHED_GETCPU
41 #include <sys/syscall.h>
42 #define __getcpu(cpu, node, cache) syscall(__NR_getcpu, cpu, node, cache)
43 /*
44 * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
45 */
46 static inline
47 int lttng_ust_get_cpu_internal(void)
48 {
49 int cpu, ret;
50
51 ret = __getcpu(&cpu, NULL, NULL);
52 if (caa_unlikely(ret < 0))
53 return 0;
54 return cpu;
55 }
56 #else /* HAVE_SCHED_GETCPU */
57 #include <sched.h>
58
59 /*
60 * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
61 */
62 static inline
63 int lttng_ust_get_cpu_internal(void)
64 {
65 int cpu;
66
67 cpu = sched_getcpu();
68 if (caa_unlikely(cpu < 0))
69 return 0;
70 return cpu;
71 }
72 #endif /* HAVE_SCHED_GETCPU */
73
74 #elif (defined(__FreeBSD__) || defined(__CYGWIN__))
75
76 /*
77 * FreeBSD and Cygwin do not allow query of CPU ID. Always use CPU
78 * number 0, with the assocated performance degradation on SMP.
79 */
80 static inline
81 int lttng_ust_get_cpu_internal(void)
82 {
83 return 0;
84 }
85
86 #else
87 #error "Please add support for your OS into liblttng-ust/compat.h."
88 #endif
89
90 #endif
91
92 static inline
93 int lttng_ust_get_cpu(void)
94 {
95 int (*getcpu)(void) = CMM_LOAD_SHARED(lttng_get_cpu);
96
97 if (caa_likely(!getcpu)) {
98 return lttng_ust_get_cpu_internal();
99 } else {
100 return getcpu();
101 }
102 }
103
104 #endif /* _LTTNG_GETCPU_H */
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