src/common/smp.h

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  */
   6
   7 #ifndef _UST_COMMON_SMP_H
   8 #define _UST_COMMON_SMP_H
   9
  10 #define LTTNG_UST_CPUMASK_SIZE 4096
  11
  12 /*
  13  * Get a CPU mask string from sysfs.
  14  *
  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.
  18  *
  19  * Returns the number of bytes read or -1 on error.
  20  */
  21 int get_cpu_mask_from_sysfs(char *buf, size_t max_bytes, const char *path)
  22         __attribute__((visibility("hidden")));
  23
  24 /*
  25  * Get the CPU possible mask string from sysfs.
  26  *
  27  * buf: the buffer where the mask will be read.
  28  * max_bytes: the maximum number of bytes to write in the buffer.
  29  *
  30  * Returns the number of bytes read or -1 on error.
  31  */
  32 int get_possible_cpu_mask_from_sysfs(char *buf, size_t max_bytes)
  33         __attribute__((visibility("hidden")));
  34
  35 /*
  36  * Get the highest CPU id from sysfs.
  37  *
  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.
  41  *
  42  * Returns the highest CPU id, or -1 on error.
  43  */
  44 int get_max_cpuid_from_sysfs(void)
  45         __attribute__((visibility("hidden")));
  46
  47 int _get_max_cpuid_from_sysfs(const char *path)
  48         __attribute__((visibility("hidden")));
  49
  50 /*
  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.
  53  *
  54  * Returns the number of possible CPUs in the system or 0 on error.
  55  */
  56 int get_num_possible_cpus_fallback(void)
  57         __attribute__((visibility("hidden")));
  58
  59 /*
  60  * Get the highest CPU id from a CPU mask.
  61  *
  62  * pmask: the mask to parse.
  63  * len: the len of the mask excluding '\0'.
  64  *
  65  * Returns the highest CPU id from the mask or -1 on error.
  66  */
  67 int get_max_cpuid_from_mask(const char *pmask, size_t len)
  68         __attribute__((visibility("hidden")));
  69
  70 /*
  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.
  73  *
  74  * We currently assume CPU ids are contiguous up the maximum CPU id.
  75  *
  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.
  78  *
  79  * If all methods fail, don't populate the cache and return 0.
  80  */
  81 int get_possible_cpus_array_len(void)
  82         __attribute__((visibility("hidden")));
  83
  84 #define for_each_possible_cpu(cpu)              \
  85         for ((cpu) = 0; (cpu) < get_possible_cpus_array_len(); (cpu)++)
  86
  87 #endif /* _UST_COMMON_SMP_H */