2 * SPDX-License-Identifier: LGPL-2.1-only
4 * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
7 #ifndef _UST_COMMON_SMP_H
8 #define _UST_COMMON_SMP_H
10 #define LTTNG_UST_CPUMASK_SIZE 4096
13 * Get a CPU mask string from sysfs.
15 * buf: the buffer where the mask will be read.
16 * max_bytes: the maximum number of bytes to write in the buffer.
17 * path: file path to read the mask from.
19 * Returns the number of bytes read or -1 on error.
21 int get_cpu_mask_from_sysfs(char *buf
, size_t max_bytes
, const char *path
)
22 __attribute__((visibility("hidden")));
25 * Get the CPU possible mask string from sysfs.
27 * buf: the buffer where the mask will be read.
28 * max_bytes: the maximum number of bytes to write in the buffer.
30 * Returns the number of bytes read or -1 on error.
32 int get_possible_cpu_mask_from_sysfs(char *buf
, size_t max_bytes
)
33 __attribute__((visibility("hidden")));
36 * Get the highest CPU id from sysfs.
38 * Iterate on all the folders in "/sys/devices/system/cpu" that start with
39 * "cpu" followed by an integer, keep the highest CPU id encountered during
40 * this iteration and add 1 to get a number of CPUs.
42 * Returns the highest CPU id, or -1 on error.
44 int get_max_cpuid_from_sysfs(void)
45 __attribute__((visibility("hidden")));
47 int _get_max_cpuid_from_sysfs(const char *path
)
48 __attribute__((visibility("hidden")));
51 * Get the number of possible CPUs in the system from either
52 * sysconf(_SC_NPROCESSORS_CONF) or some other mechanism depending on the libc.
54 * Returns the number of possible CPUs in the system or 0 on error.
56 int get_num_possible_cpus_fallback(void)
57 __attribute__((visibility("hidden")));
60 * Get the highest CPU id from a CPU mask.
62 * pmask: the mask to parse.
63 * len: the len of the mask excluding '\0'.
65 * Returns the highest CPU id from the mask or -1 on error.
67 int get_max_cpuid_from_mask(const char *pmask
, size_t len
)
68 __attribute__((visibility("hidden")));
71 * Returns the length of an array that could contain a per-CPU element for each
72 * possible CPU id for the lifetime of the process.
74 * We currently assume CPU ids are contiguous up the maximum CPU id.
76 * If the cache is not yet initialized, get the value from
77 * "/sys/devices/system/cpu/possible" or fallback to sysconf and cache it.
79 * If all methods fail, don't populate the cache and return 0.
81 int get_possible_cpus_array_len(void)
82 __attribute__((visibility("hidden")));
84 #define for_each_possible_cpu(cpu) \
85 for ((cpu) = 0; (cpu) < get_possible_cpus_array_len(); (cpu)++)
87 #endif /* _UST_COMMON_SMP_H */
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