Commit | Line | Data |
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a6352fd4 | 1 | /* |
4318ae1b | 2 | * libringbuffer/smp.c |
a6352fd4 | 3 | * |
e92f3e28 | 4 | * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
5de7c318 | 5 | * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com> |
a6352fd4 | 6 | * |
e92f3e28 MD |
7 | * This library is free software; you can redistribute it and/or |
8 | * modify it under the terms of the GNU Lesser General Public | |
9 | * License as published by the Free Software Foundation; only | |
10 | * version 2.1 of the License. | |
11 | * | |
12 | * This library is distributed in the hope that it will be useful, | |
13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | * Lesser General Public License for more details. | |
16 | * | |
17 | * You should have received a copy of the GNU Lesser General Public | |
18 | * License along with this library; if not, write to the Free Software | |
19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
a6352fd4 MD |
20 | */ |
21 | ||
5ad63a16 | 22 | #define _GNU_SOURCE |
3fbec7dc | 23 | #define _LGPL_SOURCE |
23aee768 MJ |
24 | #include <assert.h> |
25 | #include <ctype.h> | |
26 | #include <errno.h> | |
27 | #include <fcntl.h> | |
28 | #include <limits.h> | |
a6352fd4 | 29 | #include <pthread.h> |
23aee768 MJ |
30 | #include <stdlib.h> |
31 | #include <unistd.h> | |
32 | ||
a6352fd4 | 33 | #include "smp.h" |
23aee768 | 34 | #include "usterr-signal-safe.h" |
a6352fd4 MD |
35 | |
36 | int __num_possible_cpus; | |
37 | ||
5de7c318 | 38 | #if (defined(__GLIBC__) || defined( __UCLIBC__)) |
23aee768 | 39 | int get_num_possible_cpus_fallback(void) |
a6352fd4 | 40 | { |
a6352fd4 MD |
41 | /* On Linux, when some processors are offline |
42 | * _SC_NPROCESSORS_CONF counts the offline | |
43 | * processors, whereas _SC_NPROCESSORS_ONLN | |
44 | * does not. If we used _SC_NPROCESSORS_ONLN, | |
45 | * getcpu() could return a value greater than | |
46 | * this sysconf, in which case the arrays | |
47 | * indexed by processor would overflow. | |
48 | */ | |
23aee768 | 49 | return sysconf(_SC_NPROCESSORS_CONF); |
a6352fd4 | 50 | } |
5de7c318 MJ |
51 | |
52 | #else | |
53 | ||
54 | /* | |
55 | * The MUSL libc implementation of the _SC_NPROCESSORS_CONF sysconf does not | |
56 | * return the number of configured CPUs in the system but relies on the cpu | |
57 | * affinity mask of the current task. | |
58 | * | |
59 | * So instead we use a strategy similar to GLIBC's, counting the cpu | |
60 | * directories in "/sys/devices/system/cpu" and fallback on the value from | |
61 | * sysconf if it fails. | |
62 | */ | |
63 | ||
64 | #include <dirent.h> | |
65 | #include <limits.h> | |
66 | #include <stdlib.h> | |
67 | #include <string.h> | |
68 | #include <sys/types.h> | |
69 | ||
70 | #define __max(a,b) ((a)>(b)?(a):(b)) | |
71 | ||
23aee768 | 72 | int get_num_possible_cpus_fallback(void) |
5de7c318 | 73 | { |
23aee768 | 74 | int count = 0; |
5de7c318 MJ |
75 | DIR *cpudir; |
76 | struct dirent *entry; | |
77 | ||
78 | cpudir = opendir("/sys/devices/system/cpu"); | |
79 | if (cpudir == NULL) | |
80 | goto end; | |
81 | ||
82 | /* | |
83 | * Count the number of directories named "cpu" followed by and | |
84 | * integer. This is the same strategy as glibc uses. | |
85 | */ | |
86 | while ((entry = readdir(cpudir))) { | |
87 | if (entry->d_type == DT_DIR && | |
88 | strncmp(entry->d_name, "cpu", 3) == 0) { | |
89 | ||
90 | char *endptr; | |
91 | unsigned long cpu_num; | |
92 | ||
93 | cpu_num = strtoul(entry->d_name + 3, &endptr, 10); | |
94 | if ((cpu_num < ULONG_MAX) && (endptr != entry->d_name + 3) | |
95 | && (*endptr == '\0')) { | |
96 | count++; | |
97 | } | |
98 | } | |
99 | } | |
100 | ||
101 | end: | |
102 | /* | |
103 | * Get the sysconf value as a fallback. Keep the highest number. | |
104 | */ | |
23aee768 MJ |
105 | return __max(sysconf(_SC_NPROCESSORS_CONF), count); |
106 | } | |
107 | #endif | |
108 | ||
109 | /* | |
110 | * Get the CPU possible mask string from sysfs. | |
111 | * | |
112 | * buf: the buffer where the mask will be read. | |
113 | * max_bytes: the maximum number of bytes to write in the buffer. | |
114 | * | |
115 | * Returns the number of bytes read or -1 on error. | |
116 | */ | |
117 | int get_possible_cpu_mask_from_sysfs(char *buf, size_t max_bytes) | |
118 | { | |
119 | ssize_t bytes_read = 0; | |
120 | size_t total_bytes_read = 0; | |
121 | int fd = -1, ret = -1; | |
122 | ||
123 | if (buf == NULL) | |
124 | goto end; | |
125 | ||
126 | fd = open("/sys/devices/system/cpu/possible", O_RDONLY); | |
127 | if (fd < 0) | |
128 | goto end; | |
129 | ||
130 | do { | |
131 | bytes_read = read(fd, buf + total_bytes_read, | |
132 | max_bytes - total_bytes_read); | |
133 | ||
134 | if (bytes_read < 0) { | |
135 | if (errno == EINTR) { | |
136 | continue; /* retry operation */ | |
137 | } else { | |
138 | goto end; | |
139 | } | |
140 | } | |
141 | ||
142 | total_bytes_read += bytes_read; | |
143 | assert(total_bytes_read <= max_bytes); | |
144 | } while (max_bytes > total_bytes_read && bytes_read > 0); | |
145 | ||
146 | /* | |
147 | * Make sure the mask read is a null terminated string. | |
148 | */ | |
149 | if (total_bytes_read < max_bytes) | |
150 | buf[total_bytes_read] = '\0'; | |
151 | else | |
152 | buf[max_bytes - 1] = '\0'; | |
153 | ||
154 | if (total_bytes_read > INT_MAX) | |
155 | goto end; | |
156 | ||
157 | ret = (int) total_bytes_read; | |
158 | ||
159 | end: | |
160 | if (fd >= 0 && close(fd) < 0) | |
161 | PERROR("close"); | |
162 | ||
163 | return ret; | |
164 | } | |
165 | ||
166 | /* | |
167 | * Get the number of CPUs from the possible cpu mask. | |
168 | * | |
169 | * pmask: the mask to parse. | |
170 | * len: the len of the mask excluding '\0'. | |
171 | * | |
172 | * Returns the number of possible CPUs from the mask or 0 on error. | |
173 | */ | |
174 | int get_num_possible_cpus_from_mask(const char *pmask, size_t len) | |
175 | { | |
176 | ssize_t i; | |
177 | unsigned long cpu_index; | |
178 | char *endptr; | |
179 | ||
180 | /* We need at least one char to read */ | |
181 | if (len < 1) | |
182 | goto error; | |
183 | ||
184 | /* Start from the end to read the last CPU index. */ | |
185 | for (i = len - 1; i > 0; i--) { | |
186 | /* Break when we hit the first separator. */ | |
187 | if ((pmask[i] == ',') || (pmask[i] == '-')) { | |
188 | i++; | |
189 | break; | |
190 | } | |
191 | } | |
192 | ||
193 | cpu_index = strtoul(&pmask[i], &endptr, 10); | |
5de7c318 MJ |
194 | |
195 | /* | |
23aee768 MJ |
196 | * If we read a CPU index, increment it by one to return a number of |
197 | * CPUs. | |
5de7c318 | 198 | */ |
23aee768 MJ |
199 | if ((&pmask[i] != endptr) && (cpu_index < INT_MAX)) |
200 | return (int) cpu_index + 1; | |
201 | ||
202 | error: | |
203 | return 0; | |
204 | } | |
205 | ||
206 | void _get_num_possible_cpus(void) | |
207 | { | |
208 | int ret; | |
209 | int buf_len = sysconf(_SC_PAGE_SIZE); | |
210 | char buf[buf_len]; | |
211 | ||
212 | /* Get the possible cpu mask from sysfs, fallback to sysconf. */ | |
213 | ret = get_possible_cpu_mask_from_sysfs((char *) &buf, buf_len); | |
214 | if (ret <= 0) | |
215 | goto fallback; | |
216 | ||
217 | /* Parse the possible cpu mask, on failure fallback to sysconf. */ | |
218 | ret = get_num_possible_cpus_from_mask((char *) &buf, ret); | |
219 | if (ret > 0) | |
220 | goto end; | |
221 | ||
222 | fallback: | |
223 | /* Fallback to sysconf. */ | |
224 | ret = get_num_possible_cpus_fallback(); | |
225 | ||
226 | end: | |
227 | /* If all methods failed, don't store the value. */ | |
228 | if (ret < 1) | |
5de7c318 | 229 | return; |
23aee768 MJ |
230 | |
231 | __num_possible_cpus = ret; | |
5de7c318 | 232 | } |