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5cfe81b7 MJ |
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 | #include <assert.h> | |
9 | #include <ctype.h> | |
10 | #include <dirent.h> | |
11 | #include <errno.h> | |
12 | #include <fcntl.h> | |
13 | #include <limits.h> | |
14 | #include <pthread.h> | |
15 | #include <stdio.h> | |
16 | #include <stdlib.h> | |
17 | #include <string.h> | |
18 | #include <unistd.h> | |
19 | ||
20 | #include <urcu/compiler.h> | |
21 | ||
22 | #define URCU_CPUMASK_SIZE 4096 | |
23 | ||
24 | #if defined(HAVE_SYSCONF) | |
25 | static inline int get_num_possible_cpus_sysconf(void) | |
26 | { | |
27 | return sysconf(_SC_NPROCESSORS_CONF); | |
28 | } | |
29 | #else | |
30 | /* | |
31 | * On platforms without sysconf(), always return -1. | |
32 | */ | |
33 | static inline int get_num_possible_cpus_sysconf(void) | |
34 | { | |
35 | return -1; | |
36 | } | |
37 | #endif | |
38 | ||
da44a943 | 39 | #ifdef __linux__ |
5cfe81b7 MJ |
40 | /* |
41 | * Get the highest CPU id from sysfs. | |
42 | * | |
43 | * Iterate on all the folders in "/sys/devices/system/cpu" that start with | |
44 | * "cpu" followed by an integer, keep the highest CPU id encountered during | |
45 | * this iteration and add 1 to get a number of CPUs. | |
46 | * | |
47 | * Returns the highest CPU id, or -1 on error. | |
48 | */ | |
49 | static inline int _get_max_cpuid_from_sysfs(const char *path) | |
50 | { | |
51 | long max_cpuid = -1; | |
52 | ||
53 | DIR *cpudir; | |
54 | struct dirent *entry; | |
55 | ||
56 | assert(path); | |
57 | ||
58 | cpudir = opendir(path); | |
59 | if (cpudir == NULL) | |
60 | goto end; | |
61 | ||
62 | /* | |
63 | * Iterate on all directories named "cpu" followed by an integer. | |
64 | */ | |
65 | while ((entry = readdir(cpudir))) { | |
66 | if (entry->d_type == DT_DIR && | |
67 | strncmp(entry->d_name, "cpu", 3) == 0) { | |
68 | ||
69 | char *endptr; | |
70 | long cpu_id; | |
71 | ||
72 | cpu_id = strtol(entry->d_name + 3, &endptr, 10); | |
73 | if ((cpu_id < LONG_MAX) && (endptr != entry->d_name + 3) | |
74 | && (*endptr == '\0')) { | |
75 | if (cpu_id > max_cpuid) | |
76 | max_cpuid = cpu_id; | |
77 | } | |
78 | } | |
79 | } | |
80 | ||
81 | if (closedir(cpudir)) | |
82 | perror("closedir"); | |
83 | ||
84 | /* | |
85 | * If the max CPU id is out of bound, set it to -1 so it results in a | |
86 | * CPU num of 0. | |
87 | */ | |
88 | if (max_cpuid < 0 || max_cpuid > INT_MAX) | |
89 | max_cpuid = -1; | |
90 | ||
91 | end: | |
92 | return max_cpuid; | |
93 | } | |
94 | ||
95 | static inline int get_max_cpuid_from_sysfs(void) | |
96 | { | |
97 | return _get_max_cpuid_from_sysfs("/sys/devices/system/cpu"); | |
98 | } | |
99 | ||
100 | ||
101 | /* | |
102 | * As a fallback to parsing the CPU mask in "/sys/devices/system/cpu/possible", | |
103 | * iterate on all the folders in "/sys/devices/system/cpu" that start with | |
104 | * "cpu" followed by an integer, keep the highest CPU id encountered during | |
105 | * this iteration and add 1 to get a number of CPUs. | |
106 | * | |
107 | * Then get the value from sysconf(_SC_NPROCESSORS_CONF) as a fallback and | |
108 | * return the highest one. | |
109 | * | |
110 | * On Linux, using the value from sysconf can be unreliable since the way it | |
111 | * counts CPUs varies between C libraries and even between versions of the same | |
112 | * library. If we used it directly, getcpu() could return a value greater than | |
113 | * this sysconf, in which case the arrays indexed by processor would overflow. | |
114 | * | |
115 | * As another example, the MUSL libc implementation of the _SC_NPROCESSORS_CONF | |
116 | * sysconf does not return the number of configured CPUs in the system but | |
117 | * relies on the cpu affinity mask of the current task. | |
118 | * | |
119 | * Returns 0 or less on error. | |
120 | */ | |
121 | static inline int get_num_possible_cpus_fallback(void) | |
122 | { | |
123 | /* | |
124 | * Get the sysconf value as a last resort. Keep the highest number. | |
125 | */ | |
126 | return caa_max(get_num_possible_cpus_sysconf(), get_max_cpuid_from_sysfs() + 1); | |
127 | } | |
128 | ||
129 | /* | |
130 | * Get a CPU mask string from sysfs. | |
131 | * | |
132 | * buf: the buffer where the mask will be read. | |
133 | * max_bytes: the maximum number of bytes to write in the buffer. | |
134 | * path: file path to read the mask from. | |
135 | * | |
136 | * Returns the number of bytes read or -1 on error. | |
137 | */ | |
138 | static inline int get_cpu_mask_from_sysfs(char *buf, size_t max_bytes, const char *path) | |
139 | { | |
140 | ssize_t bytes_read = 0; | |
141 | size_t total_bytes_read = 0; | |
142 | int fd = -1, ret = -1; | |
143 | ||
144 | assert(path); | |
145 | ||
146 | if (buf == NULL) | |
147 | goto end; | |
148 | ||
149 | fd = open(path, O_RDONLY); | |
150 | if (fd < 0) | |
151 | goto end; | |
152 | ||
153 | do { | |
154 | bytes_read = read(fd, buf + total_bytes_read, | |
155 | max_bytes - total_bytes_read); | |
156 | ||
157 | if (bytes_read < 0) { | |
158 | if (errno == EINTR) { | |
159 | continue; /* retry operation */ | |
160 | } else { | |
161 | goto end; | |
162 | } | |
163 | } | |
164 | ||
165 | total_bytes_read += bytes_read; | |
166 | assert(total_bytes_read <= max_bytes); | |
167 | } while (max_bytes > total_bytes_read && bytes_read > 0); | |
168 | ||
169 | /* | |
170 | * Make sure the mask read is a null terminated string. | |
171 | */ | |
172 | if (total_bytes_read < max_bytes) | |
173 | buf[total_bytes_read] = '\0'; | |
174 | else | |
175 | buf[max_bytes - 1] = '\0'; | |
176 | ||
177 | if (total_bytes_read > INT_MAX) | |
178 | goto end; | |
179 | ||
180 | ret = (int) total_bytes_read; | |
181 | ||
182 | end: | |
183 | if (fd >= 0 && close(fd) < 0) | |
184 | perror("close"); | |
185 | ||
186 | return ret; | |
187 | } | |
188 | ||
189 | /* | |
190 | * Get the CPU possible mask string from sysfs. | |
191 | * | |
192 | * buf: the buffer where the mask will be read. | |
193 | * max_bytes: the maximum number of bytes to write in the buffer. | |
194 | * | |
195 | * Returns the number of bytes read or -1 on error. | |
196 | */ | |
197 | static inline int get_possible_cpu_mask_from_sysfs(char *buf, size_t max_bytes) | |
198 | { | |
199 | return get_cpu_mask_from_sysfs(buf, max_bytes, | |
200 | "/sys/devices/system/cpu/possible"); | |
201 | } | |
202 | ||
203 | /* | |
204 | * Get the highest CPU id from the possible CPU mask. | |
205 | * | |
206 | * pmask: the mask to parse. | |
207 | * len: the len of the mask excluding '\0'. | |
208 | * | |
209 | * Returns the highest CPU id from the mask or -1 on error. | |
210 | */ | |
211 | static inline int get_max_cpuid_from_mask(const char *pmask, size_t len) | |
212 | { | |
213 | ssize_t i; | |
214 | unsigned long cpu_index; | |
215 | char *endptr; | |
216 | ||
217 | /* We need at least one char to read */ | |
218 | if (len < 1) | |
219 | goto error; | |
220 | ||
221 | /* Start from the end to read the last CPU index. */ | |
222 | for (i = len - 1; i > 0; i--) { | |
223 | /* Break when we hit the first separator. */ | |
224 | if ((pmask[i] == ',') || (pmask[i] == '-')) { | |
225 | i++; | |
226 | break; | |
227 | } | |
228 | } | |
229 | ||
230 | cpu_index = strtoul(&pmask[i], &endptr, 10); | |
231 | ||
232 | if ((&pmask[i] != endptr) && (cpu_index < INT_MAX)) | |
233 | return (int) cpu_index; | |
234 | ||
235 | error: | |
236 | return -1; | |
237 | } | |
238 | ||
5cfe81b7 MJ |
239 | /* |
240 | * On Linux try sysfs first and fallback to sysconf. | |
241 | */ | |
242 | static inline int get_possible_cpus_array_len(void) | |
243 | { | |
244 | int ret; | |
245 | char buf[URCU_CPUMASK_SIZE]; | |
246 | ||
247 | /* Get the possible cpu mask from sysfs, fallback to sysconf. */ | |
248 | ret = get_possible_cpu_mask_from_sysfs((char *) &buf, URCU_CPUMASK_SIZE); | |
249 | if (ret <= 0) | |
250 | goto fallback; | |
251 | ||
252 | /* Parse the possible cpu mask, on failure fallback to sysconf. */ | |
253 | ret = get_max_cpuid_from_mask((char *) &buf, ret); | |
254 | if (ret >= 0) { | |
255 | /* Add 1 to convert from max cpuid to an array len. */ | |
256 | ret++; | |
257 | goto end; | |
258 | } | |
259 | ||
260 | fallback: | |
261 | /* Fallback to sysconf. */ | |
262 | ret = get_num_possible_cpus_fallback(); | |
263 | ||
264 | end: | |
265 | return ret; | |
266 | } | |
267 | #else | |
268 | /* | |
269 | * On other platforms, only use sysconf. | |
270 | */ | |
271 | static inline int get_possible_cpus_array_len(void) | |
272 | { | |
273 | return get_num_possible_cpus_sysconf(); | |
274 | } | |
275 | #endif |