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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 | ||
39 | /* | |
40 | * Get the highest CPU id from sysfs. | |
41 | * | |
42 | * Iterate on all the folders in "/sys/devices/system/cpu" that start with | |
43 | * "cpu" followed by an integer, keep the highest CPU id encountered during | |
44 | * this iteration and add 1 to get a number of CPUs. | |
45 | * | |
46 | * Returns the highest CPU id, or -1 on error. | |
47 | */ | |
48 | static inline int _get_max_cpuid_from_sysfs(const char *path) | |
49 | { | |
50 | long max_cpuid = -1; | |
51 | ||
52 | DIR *cpudir; | |
53 | struct dirent *entry; | |
54 | ||
55 | assert(path); | |
56 | ||
57 | cpudir = opendir(path); | |
58 | if (cpudir == NULL) | |
59 | goto end; | |
60 | ||
61 | /* | |
62 | * Iterate on all directories named "cpu" followed by an integer. | |
63 | */ | |
64 | while ((entry = readdir(cpudir))) { | |
65 | if (entry->d_type == DT_DIR && | |
66 | strncmp(entry->d_name, "cpu", 3) == 0) { | |
67 | ||
68 | char *endptr; | |
69 | long cpu_id; | |
70 | ||
71 | cpu_id = strtol(entry->d_name + 3, &endptr, 10); | |
72 | if ((cpu_id < LONG_MAX) && (endptr != entry->d_name + 3) | |
73 | && (*endptr == '\0')) { | |
74 | if (cpu_id > max_cpuid) | |
75 | max_cpuid = cpu_id; | |
76 | } | |
77 | } | |
78 | } | |
79 | ||
80 | if (closedir(cpudir)) | |
81 | perror("closedir"); | |
82 | ||
83 | /* | |
84 | * If the max CPU id is out of bound, set it to -1 so it results in a | |
85 | * CPU num of 0. | |
86 | */ | |
87 | if (max_cpuid < 0 || max_cpuid > INT_MAX) | |
88 | max_cpuid = -1; | |
89 | ||
90 | end: | |
91 | return max_cpuid; | |
92 | } | |
93 | ||
94 | static inline int get_max_cpuid_from_sysfs(void) | |
95 | { | |
96 | return _get_max_cpuid_from_sysfs("/sys/devices/system/cpu"); | |
97 | } | |
98 | ||
99 | ||
100 | /* | |
101 | * As a fallback to parsing the CPU mask in "/sys/devices/system/cpu/possible", | |
102 | * iterate on all the folders in "/sys/devices/system/cpu" that start with | |
103 | * "cpu" followed by an integer, keep the highest CPU id encountered during | |
104 | * this iteration and add 1 to get a number of CPUs. | |
105 | * | |
106 | * Then get the value from sysconf(_SC_NPROCESSORS_CONF) as a fallback and | |
107 | * return the highest one. | |
108 | * | |
109 | * On Linux, using the value from sysconf can be unreliable since the way it | |
110 | * counts CPUs varies between C libraries and even between versions of the same | |
111 | * library. If we used it directly, getcpu() could return a value greater than | |
112 | * this sysconf, in which case the arrays indexed by processor would overflow. | |
113 | * | |
114 | * As another example, the MUSL libc implementation of the _SC_NPROCESSORS_CONF | |
115 | * sysconf does not return the number of configured CPUs in the system but | |
116 | * relies on the cpu affinity mask of the current task. | |
117 | * | |
118 | * Returns 0 or less on error. | |
119 | */ | |
120 | static inline int get_num_possible_cpus_fallback(void) | |
121 | { | |
122 | /* | |
123 | * Get the sysconf value as a last resort. Keep the highest number. | |
124 | */ | |
125 | return caa_max(get_num_possible_cpus_sysconf(), get_max_cpuid_from_sysfs() + 1); | |
126 | } | |
127 | ||
128 | /* | |
129 | * Get a CPU mask string from sysfs. | |
130 | * | |
131 | * buf: the buffer where the mask will be read. | |
132 | * max_bytes: the maximum number of bytes to write in the buffer. | |
133 | * path: file path to read the mask from. | |
134 | * | |
135 | * Returns the number of bytes read or -1 on error. | |
136 | */ | |
137 | static inline int get_cpu_mask_from_sysfs(char *buf, size_t max_bytes, const char *path) | |
138 | { | |
139 | ssize_t bytes_read = 0; | |
140 | size_t total_bytes_read = 0; | |
141 | int fd = -1, ret = -1; | |
142 | ||
143 | assert(path); | |
144 | ||
145 | if (buf == NULL) | |
146 | goto end; | |
147 | ||
148 | fd = open(path, O_RDONLY); | |
149 | if (fd < 0) | |
150 | goto end; | |
151 | ||
152 | do { | |
153 | bytes_read = read(fd, buf + total_bytes_read, | |
154 | max_bytes - total_bytes_read); | |
155 | ||
156 | if (bytes_read < 0) { | |
157 | if (errno == EINTR) { | |
158 | continue; /* retry operation */ | |
159 | } else { | |
160 | goto end; | |
161 | } | |
162 | } | |
163 | ||
164 | total_bytes_read += bytes_read; | |
165 | assert(total_bytes_read <= max_bytes); | |
166 | } while (max_bytes > total_bytes_read && bytes_read > 0); | |
167 | ||
168 | /* | |
169 | * Make sure the mask read is a null terminated string. | |
170 | */ | |
171 | if (total_bytes_read < max_bytes) | |
172 | buf[total_bytes_read] = '\0'; | |
173 | else | |
174 | buf[max_bytes - 1] = '\0'; | |
175 | ||
176 | if (total_bytes_read > INT_MAX) | |
177 | goto end; | |
178 | ||
179 | ret = (int) total_bytes_read; | |
180 | ||
181 | end: | |
182 | if (fd >= 0 && close(fd) < 0) | |
183 | perror("close"); | |
184 | ||
185 | return ret; | |
186 | } | |
187 | ||
188 | /* | |
189 | * Get the CPU possible mask string from sysfs. | |
190 | * | |
191 | * buf: the buffer where the mask will be read. | |
192 | * max_bytes: the maximum number of bytes to write in the buffer. | |
193 | * | |
194 | * Returns the number of bytes read or -1 on error. | |
195 | */ | |
196 | static inline int get_possible_cpu_mask_from_sysfs(char *buf, size_t max_bytes) | |
197 | { | |
198 | return get_cpu_mask_from_sysfs(buf, max_bytes, | |
199 | "/sys/devices/system/cpu/possible"); | |
200 | } | |
201 | ||
202 | /* | |
203 | * Get the highest CPU id from the possible CPU mask. | |
204 | * | |
205 | * pmask: the mask to parse. | |
206 | * len: the len of the mask excluding '\0'. | |
207 | * | |
208 | * Returns the highest CPU id from the mask or -1 on error. | |
209 | */ | |
210 | static inline int get_max_cpuid_from_mask(const char *pmask, size_t len) | |
211 | { | |
212 | ssize_t i; | |
213 | unsigned long cpu_index; | |
214 | char *endptr; | |
215 | ||
216 | /* We need at least one char to read */ | |
217 | if (len < 1) | |
218 | goto error; | |
219 | ||
220 | /* Start from the end to read the last CPU index. */ | |
221 | for (i = len - 1; i > 0; i--) { | |
222 | /* Break when we hit the first separator. */ | |
223 | if ((pmask[i] == ',') || (pmask[i] == '-')) { | |
224 | i++; | |
225 | break; | |
226 | } | |
227 | } | |
228 | ||
229 | cpu_index = strtoul(&pmask[i], &endptr, 10); | |
230 | ||
231 | if ((&pmask[i] != endptr) && (cpu_index < INT_MAX)) | |
232 | return (int) cpu_index; | |
233 | ||
234 | error: | |
235 | return -1; | |
236 | } | |
237 | ||
238 | #ifdef __linux__ | |
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 |