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> |
13d2c5ba | 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 |
f1d40e23 MJ |
24 | #include <assert.h> |
25 | #include <ctype.h> | |
94b4db5a | 26 | #include <dirent.h> |
f1d40e23 MJ |
27 | #include <errno.h> |
28 | #include <fcntl.h> | |
29 | #include <limits.h> | |
a6352fd4 | 30 | #include <pthread.h> |
f1d40e23 MJ |
31 | #include <stdlib.h> |
32 | #include <unistd.h> | |
94b4db5a MJ |
33 | #include <string.h> |
34 | #include <sys/types.h> | |
f1d40e23 | 35 | |
a6352fd4 | 36 | #include "smp.h" |
f1d40e23 | 37 | #include "usterr-signal-safe.h" |
a6352fd4 | 38 | |
94b4db5a | 39 | #define __max(a,b) ((a)>(b)?(a):(b)) |
13d2c5ba | 40 | |
94b4db5a | 41 | int __num_possible_cpus; |
13d2c5ba MJ |
42 | |
43 | /* | |
94b4db5a MJ |
44 | * As a fallback to parsing the CPU mask in "/sys/devices/system/cpu/possible", |
45 | * iterate on all the folders in "/sys/devices/system/cpu" that start with | |
46 | * "cpu" followed by an integer, keep the highest CPU id encountered during | |
47 | * this iteration and add 1 to get a number of CPUs. | |
48 | * | |
49 | * Then get the value from sysconf(_SC_NPROCESSORS_CONF) as a fallback and | |
50 | * return the highest one. | |
51 | * | |
52 | * On Linux, using the value from sysconf can be unreliable since the way it | |
53 | * counts CPUs varies between C libraries and even between versions of the same | |
54 | * library. If we used it directly, getcpu() could return a value greater than | |
55 | * this sysconf, in which case the arrays indexed by processor would overflow. | |
56 | * | |
57 | * As another example, the MUSL libc implementation of the _SC_NPROCESSORS_CONF | |
58 | * sysconf does not return the number of configured CPUs in the system but | |
59 | * relies on the cpu affinity mask of the current task. | |
13d2c5ba | 60 | * |
94b4db5a | 61 | * Returns 0 or less on error. |
13d2c5ba | 62 | */ |
f1d40e23 | 63 | int get_num_possible_cpus_fallback(void) |
13d2c5ba | 64 | { |
94b4db5a MJ |
65 | long max_cpuid = -1; |
66 | ||
13d2c5ba MJ |
67 | DIR *cpudir; |
68 | struct dirent *entry; | |
69 | ||
70 | cpudir = opendir("/sys/devices/system/cpu"); | |
71 | if (cpudir == NULL) | |
72 | goto end; | |
73 | ||
74 | /* | |
94b4db5a | 75 | * Iterate on all directories named "cpu" followed by an integer. |
13d2c5ba MJ |
76 | */ |
77 | while ((entry = readdir(cpudir))) { | |
78 | if (entry->d_type == DT_DIR && | |
79 | strncmp(entry->d_name, "cpu", 3) == 0) { | |
80 | ||
81 | char *endptr; | |
94b4db5a | 82 | long cpu_id; |
13d2c5ba | 83 | |
94b4db5a MJ |
84 | cpu_id = strtol(entry->d_name + 3, &endptr, 10); |
85 | if ((cpu_id < LONG_MAX) && (endptr != entry->d_name + 3) | |
13d2c5ba | 86 | && (*endptr == '\0')) { |
94b4db5a MJ |
87 | if (cpu_id > max_cpuid) |
88 | max_cpuid = cpu_id; | |
13d2c5ba MJ |
89 | } |
90 | } | |
91 | } | |
92 | ||
94b4db5a MJ |
93 | if (closedir(cpudir)) |
94 | PERROR("closedir"); | |
95 | ||
96 | /* | |
97 | * If the max CPU id is out of bound, set it to -1 so it results in a | |
98 | * CPU num of 0. | |
99 | */ | |
100 | if (max_cpuid < 0 || max_cpuid > INT_MAX) | |
101 | max_cpuid = -1; | |
102 | ||
13d2c5ba MJ |
103 | end: |
104 | /* | |
94b4db5a | 105 | * Get the sysconf value as a last resort. Keep the highest number. |
13d2c5ba | 106 | */ |
94b4db5a | 107 | return __max(sysconf(_SC_NPROCESSORS_CONF), max_cpuid + 1); |
f1d40e23 | 108 | } |
f1d40e23 MJ |
109 | |
110 | /* | |
111 | * Get the CPU possible mask string from sysfs. | |
112 | * | |
113 | * buf: the buffer where the mask will be read. | |
114 | * max_bytes: the maximum number of bytes to write in the buffer. | |
115 | * | |
116 | * Returns the number of bytes read or -1 on error. | |
117 | */ | |
118 | int get_possible_cpu_mask_from_sysfs(char *buf, size_t max_bytes) | |
119 | { | |
120 | ssize_t bytes_read = 0; | |
121 | size_t total_bytes_read = 0; | |
122 | int fd = -1, ret = -1; | |
123 | ||
124 | if (buf == NULL) | |
125 | goto end; | |
126 | ||
127 | fd = open("/sys/devices/system/cpu/possible", O_RDONLY); | |
128 | if (fd < 0) | |
129 | goto end; | |
130 | ||
131 | do { | |
132 | bytes_read = read(fd, buf + total_bytes_read, | |
133 | max_bytes - total_bytes_read); | |
134 | ||
135 | if (bytes_read < 0) { | |
136 | if (errno == EINTR) { | |
137 | continue; /* retry operation */ | |
138 | } else { | |
139 | goto end; | |
140 | } | |
141 | } | |
142 | ||
143 | total_bytes_read += bytes_read; | |
144 | assert(total_bytes_read <= max_bytes); | |
145 | } while (max_bytes > total_bytes_read && bytes_read > 0); | |
146 | ||
147 | /* | |
148 | * Make sure the mask read is a null terminated string. | |
149 | */ | |
150 | if (total_bytes_read < max_bytes) | |
151 | buf[total_bytes_read] = '\0'; | |
152 | else | |
153 | buf[max_bytes - 1] = '\0'; | |
154 | ||
155 | if (total_bytes_read > INT_MAX) | |
156 | goto end; | |
157 | ||
158 | ret = (int) total_bytes_read; | |
159 | ||
160 | end: | |
161 | if (fd >= 0 && close(fd) < 0) | |
162 | PERROR("close"); | |
163 | ||
164 | return ret; | |
165 | } | |
166 | ||
167 | /* | |
168 | * Get the number of CPUs from the possible cpu mask. | |
169 | * | |
170 | * pmask: the mask to parse. | |
171 | * len: the len of the mask excluding '\0'. | |
172 | * | |
173 | * Returns the number of possible CPUs from the mask or 0 on error. | |
174 | */ | |
175 | int get_num_possible_cpus_from_mask(const char *pmask, size_t len) | |
176 | { | |
177 | ssize_t i; | |
178 | unsigned long cpu_index; | |
179 | char *endptr; | |
180 | ||
181 | /* We need at least one char to read */ | |
182 | if (len < 1) | |
183 | goto error; | |
184 | ||
185 | /* Start from the end to read the last CPU index. */ | |
186 | for (i = len - 1; i > 0; i--) { | |
187 | /* Break when we hit the first separator. */ | |
188 | if ((pmask[i] == ',') || (pmask[i] == '-')) { | |
189 | i++; | |
190 | break; | |
191 | } | |
192 | } | |
193 | ||
194 | cpu_index = strtoul(&pmask[i], &endptr, 10); | |
13d2c5ba MJ |
195 | |
196 | /* | |
f1d40e23 MJ |
197 | * If we read a CPU index, increment it by one to return a number of |
198 | * CPUs. | |
13d2c5ba | 199 | */ |
f1d40e23 MJ |
200 | if ((&pmask[i] != endptr) && (cpu_index < INT_MAX)) |
201 | return (int) cpu_index + 1; | |
202 | ||
203 | error: | |
204 | return 0; | |
205 | } | |
206 | ||
207 | void _get_num_possible_cpus(void) | |
208 | { | |
209 | int ret; | |
bb6e798c | 210 | char buf[LTTNG_UST_CPUMASK_SIZE]; |
f1d40e23 MJ |
211 | |
212 | /* Get the possible cpu mask from sysfs, fallback to sysconf. */ | |
bb6e798c | 213 | ret = get_possible_cpu_mask_from_sysfs((char *) &buf, LTTNG_UST_CPUMASK_SIZE); |
f1d40e23 MJ |
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) | |
13d2c5ba | 229 | return; |
f1d40e23 MJ |
230 | |
231 | __num_possible_cpus = ret; | |
13d2c5ba | 232 | } |