| 1 | /* |
| 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| 3 | * |
| 4 | * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com> |
| 6 | */ |
| 7 | |
| 8 | #define _GNU_SOURCE |
| 9 | #define _LGPL_SOURCE |
| 10 | |
| 11 | #include <unistd.h> |
| 12 | #include <pthread.h> |
| 13 | #include "smp.h" |
| 14 | |
| 15 | int __lttng_counter_num_possible_cpus; |
| 16 | |
| 17 | #if (defined(__GLIBC__) || defined( __UCLIBC__)) |
| 18 | void _lttng_counter_get_num_possible_cpus(void) |
| 19 | { |
| 20 | int result; |
| 21 | |
| 22 | /* On Linux, when some processors are offline |
| 23 | * _SC_NPROCESSORS_CONF counts the offline |
| 24 | * processors, whereas _SC_NPROCESSORS_ONLN |
| 25 | * does not. If we used _SC_NPROCESSORS_ONLN, |
| 26 | * getcpu() could return a value greater than |
| 27 | * this sysconf, in which case the arrays |
| 28 | * indexed by processor would overflow. |
| 29 | */ |
| 30 | result = sysconf(_SC_NPROCESSORS_CONF); |
| 31 | if (result == -1) |
| 32 | return; |
| 33 | __lttng_counter_num_possible_cpus = result; |
| 34 | } |
| 35 | |
| 36 | #else |
| 37 | |
| 38 | /* |
| 39 | * The MUSL libc implementation of the _SC_NPROCESSORS_CONF sysconf does not |
| 40 | * return the number of configured CPUs in the system but relies on the cpu |
| 41 | * affinity mask of the current task. |
| 42 | * |
| 43 | * So instead we use a strategy similar to GLIBC's, counting the cpu |
| 44 | * directories in "/sys/devices/system/cpu" and fallback on the value from |
| 45 | * sysconf if it fails. |
| 46 | */ |
| 47 | |
| 48 | #include <dirent.h> |
| 49 | #include <limits.h> |
| 50 | #include <stdlib.h> |
| 51 | #include <string.h> |
| 52 | #include <sys/types.h> |
| 53 | |
| 54 | #define __max(a,b) ((a)>(b)?(a):(b)) |
| 55 | |
| 56 | void _lttng_counter_get_num_possible_cpus(void) |
| 57 | { |
| 58 | int result, count = 0; |
| 59 | DIR *cpudir; |
| 60 | struct dirent *entry; |
| 61 | |
| 62 | cpudir = opendir("/sys/devices/system/cpu"); |
| 63 | if (cpudir == NULL) |
| 64 | goto end; |
| 65 | |
| 66 | /* |
| 67 | * Count the number of directories named "cpu" followed by and |
| 68 | * integer. This is the same strategy as glibc uses. |
| 69 | */ |
| 70 | while ((entry = readdir(cpudir))) { |
| 71 | if (entry->d_type == DT_DIR && |
| 72 | strncmp(entry->d_name, "cpu", 3) == 0) { |
| 73 | |
| 74 | char *endptr; |
| 75 | unsigned long cpu_num; |
| 76 | |
| 77 | cpu_num = strtoul(entry->d_name + 3, &endptr, 10); |
| 78 | if ((cpu_num < ULONG_MAX) && (endptr != entry->d_name + 3) |
| 79 | && (*endptr == '\0')) { |
| 80 | count++; |
| 81 | } |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | end: |
| 86 | /* |
| 87 | * Get the sysconf value as a fallback. Keep the highest number. |
| 88 | */ |
| 89 | result = __max(sysconf(_SC_NPROCESSORS_CONF), count); |
| 90 | |
| 91 | /* |
| 92 | * If both methods failed, don't store the value. |
| 93 | */ |
| 94 | if (result < 1) |
| 95 | return; |
| 96 | __lttng_counter_num_possible_cpus = result; |
| 97 | } |
| 98 | #endif |