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ebabbf58 | 1 | /* |
c0c0989a | 2 | * SPDX-License-Identifier: LGPL-2.1-only |
ebabbf58 MD |
3 | * |
4 | * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
5 | * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com> | |
ebabbf58 MD |
6 | */ |
7 | ||
ebabbf58 | 8 | #define _LGPL_SOURCE |
c0c0989a | 9 | |
ebabbf58 MD |
10 | #include <unistd.h> |
11 | #include <pthread.h> | |
12 | #include "smp.h" | |
13 | ||
14 | int __lttng_counter_num_possible_cpus; | |
15 | ||
16 | #if (defined(__GLIBC__) || defined( __UCLIBC__)) | |
17 | void _lttng_counter_get_num_possible_cpus(void) | |
18 | { | |
19 | int result; | |
20 | ||
21 | /* On Linux, when some processors are offline | |
22 | * _SC_NPROCESSORS_CONF counts the offline | |
23 | * processors, whereas _SC_NPROCESSORS_ONLN | |
24 | * does not. If we used _SC_NPROCESSORS_ONLN, | |
25 | * getcpu() could return a value greater than | |
26 | * this sysconf, in which case the arrays | |
27 | * indexed by processor would overflow. | |
28 | */ | |
29 | result = sysconf(_SC_NPROCESSORS_CONF); | |
30 | if (result == -1) | |
31 | return; | |
32 | __lttng_counter_num_possible_cpus = result; | |
33 | } | |
34 | ||
35 | #else | |
36 | ||
37 | /* | |
38 | * The MUSL libc implementation of the _SC_NPROCESSORS_CONF sysconf does not | |
39 | * return the number of configured CPUs in the system but relies on the cpu | |
40 | * affinity mask of the current task. | |
41 | * | |
42 | * So instead we use a strategy similar to GLIBC's, counting the cpu | |
43 | * directories in "/sys/devices/system/cpu" and fallback on the value from | |
44 | * sysconf if it fails. | |
45 | */ | |
46 | ||
47 | #include <dirent.h> | |
48 | #include <limits.h> | |
49 | #include <stdlib.h> | |
50 | #include <string.h> | |
51 | #include <sys/types.h> | |
52 | ||
53 | #define __max(a,b) ((a)>(b)?(a):(b)) | |
54 | ||
55 | void _lttng_counter_get_num_possible_cpus(void) | |
56 | { | |
57 | int result, count = 0; | |
58 | DIR *cpudir; | |
59 | struct dirent *entry; | |
60 | ||
61 | cpudir = opendir("/sys/devices/system/cpu"); | |
62 | if (cpudir == NULL) | |
63 | goto end; | |
64 | ||
65 | /* | |
66 | * Count the number of directories named "cpu" followed by and | |
67 | * integer. This is the same strategy as glibc uses. | |
68 | */ | |
69 | while ((entry = readdir(cpudir))) { | |
70 | if (entry->d_type == DT_DIR && | |
71 | strncmp(entry->d_name, "cpu", 3) == 0) { | |
72 | ||
73 | char *endptr; | |
74 | unsigned long cpu_num; | |
75 | ||
76 | cpu_num = strtoul(entry->d_name + 3, &endptr, 10); | |
77 | if ((cpu_num < ULONG_MAX) && (endptr != entry->d_name + 3) | |
78 | && (*endptr == '\0')) { | |
79 | count++; | |
80 | } | |
81 | } | |
82 | } | |
83 | ||
84 | end: | |
85 | /* | |
86 | * Get the sysconf value as a fallback. Keep the highest number. | |
87 | */ | |
88 | result = __max(sysconf(_SC_NPROCESSORS_CONF), count); | |
89 | ||
90 | /* | |
91 | * If both methods failed, don't store the value. | |
92 | */ | |
93 | if (result < 1) | |
94 | return; | |
95 | __lttng_counter_num_possible_cpus = result; | |
96 | } | |
97 | #endif |