[urcu.git] / src / compat-smp.h

/*
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
 */

#include <assert.h>
#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <urcu/compiler.h>

#define URCU_CPUMASK_SIZE 4096

#if defined(HAVE_SYSCONF)
static inline int get_num_possible_cpus_sysconf(void)
{
	return sysconf(_SC_NPROCESSORS_CONF);
}
#else
/*
 * On platforms without sysconf(), always return -1.
 */
static inline int get_num_possible_cpus_sysconf(void)
{
	return -1;
}
#endif

#ifdef __linux__
/*
 * Get the highest CPU id from sysfs.
 *
 * Iterate on all the folders in "/sys/devices/system/cpu" that start with
 * "cpu" followed by an integer, keep the highest CPU id encountered during
 * this iteration and add 1 to get a number of CPUs.
 *
 * Returns the highest CPU id, or -1 on error.
 */
static inline int _get_max_cpuid_from_sysfs(const char *path)
{
	long max_cpuid = -1;

	DIR *cpudir;
	struct dirent *entry;

	assert(path);

	cpudir = opendir(path);
	if (cpudir == NULL)
		goto end;

	/*
	 * Iterate on all directories named "cpu" followed by an integer.
	 */
	while ((entry = readdir(cpudir))) {
		if (entry->d_type == DT_DIR &&
			strncmp(entry->d_name, "cpu", 3) == 0) {

			char *endptr;
			long cpu_id;

			cpu_id = strtol(entry->d_name + 3, &endptr, 10);
			if ((cpu_id < LONG_MAX) && (endptr != entry->d_name + 3)
					&& (*endptr == '\0')) {
				if (cpu_id > max_cpuid)
					max_cpuid = cpu_id;
			}
		}
	}

	if (closedir(cpudir))
		perror("closedir");

	/*
	 * If the max CPU id is out of bound, set it to -1 so it results in a
	 * CPU num of 0.
	 */
	if (max_cpuid < 0 || max_cpuid > INT_MAX)
		max_cpuid = -1;

end:
	return max_cpuid;
}

static inline int get_max_cpuid_from_sysfs(void)
{
	return _get_max_cpuid_from_sysfs("/sys/devices/system/cpu");
}


/*
 * As a fallback to parsing the CPU mask in "/sys/devices/system/cpu/possible",
 * iterate on all the folders in "/sys/devices/system/cpu" that start with
 * "cpu" followed by an integer, keep the highest CPU id encountered during
 * this iteration and add 1 to get a number of CPUs.
 *
 * Then get the value from sysconf(_SC_NPROCESSORS_CONF) as a fallback and
 * return the highest one.
 *
 * On Linux, using the value from sysconf can be unreliable since the way it
 * counts CPUs varies between C libraries and even between versions of the same
 * library. If we used it directly, getcpu() could return a value greater than
 * this sysconf, in which case the arrays indexed by processor would overflow.
 *
 * As another example, the MUSL libc implementation of the _SC_NPROCESSORS_CONF
 * sysconf does not return the number of configured CPUs in the system but
 * relies on the cpu affinity mask of the current task.
 *
 * Returns 0 or less on error.
 */
static inline int get_num_possible_cpus_fallback(void)
{
	/*
	 * Get the sysconf value as a last resort. Keep the highest number.
	 */
	return caa_max(get_num_possible_cpus_sysconf(), get_max_cpuid_from_sysfs() + 1);
}

/*
 * Get a CPU mask string from sysfs.
 *
 * buf: the buffer where the mask will be read.
 * max_bytes: the maximum number of bytes to write in the buffer.
 * path: file path to read the mask from.
 *
 * Returns the number of bytes read or -1 on error.
 */
static inline int get_cpu_mask_from_sysfs(char *buf, size_t max_bytes, const char *path)
{
	ssize_t bytes_read = 0;
	size_t total_bytes_read = 0;
	int fd = -1, ret = -1;

	assert(path);

	if (buf == NULL)
		goto end;

	fd = open(path, O_RDONLY);
	if (fd < 0)
		goto end;

	do {
		bytes_read = read(fd, buf + total_bytes_read,
				max_bytes - total_bytes_read);

		if (bytes_read < 0) {
			if (errno == EINTR) {
				continue;	/* retry operation */
			} else {
				goto end;
			}
		}

		total_bytes_read += bytes_read;
		assert(total_bytes_read <= max_bytes);
	} while (max_bytes > total_bytes_read && bytes_read > 0);

	/*
	 * Make sure the mask read is a null terminated string.
	 */
	if (total_bytes_read < max_bytes)
		buf[total_bytes_read] = '\0';
	else
		buf[max_bytes - 1] = '\0';

	if (total_bytes_read > INT_MAX)
		goto end;

	ret = (int) total_bytes_read;

end:
	if (fd >= 0 && close(fd) < 0)
		perror("close");

	return ret;
}

/*
 * Get the CPU possible mask string from sysfs.
 *
 * buf: the buffer where the mask will be read.
 * max_bytes: the maximum number of bytes to write in the buffer.
 *
 * Returns the number of bytes read or -1 on error.
 */
static inline int get_possible_cpu_mask_from_sysfs(char *buf, size_t max_bytes)
{
	return get_cpu_mask_from_sysfs(buf, max_bytes,
			"/sys/devices/system/cpu/possible");
}

/*
 * Get the highest CPU id from the possible CPU mask.
 *
 * pmask: the mask to parse.
 * len: the len of the mask excluding '\0'.
 *
 * Returns the highest CPU id from the mask or -1 on error.
 */
static inline int get_max_cpuid_from_mask(const char *pmask, size_t len)
{
	ssize_t i;
	unsigned long cpu_index;
	char *endptr;

	/* We need at least one char to read */
	if (len < 1)
		goto error;

	/* Start from the end to read the last CPU index. */
	for (i = len - 1; i > 0; i--) {
		/* Break when we hit the first separator. */
		if ((pmask[i] == ',') || (pmask[i] == '-')) {
			i++;
			break;
		}
	}

	cpu_index = strtoul(&pmask[i], &endptr, 10);

	if ((&pmask[i] != endptr) && (cpu_index < INT_MAX))
		return (int) cpu_index;

error:
	return -1;
}

/*
 * On Linux try sysfs first and fallback to sysconf.
 */
static inline int get_possible_cpus_array_len(void)
{
	int ret;
	char buf[URCU_CPUMASK_SIZE];

	/* Get the possible cpu mask from sysfs, fallback to sysconf. */
	ret = get_possible_cpu_mask_from_sysfs((char *) &buf, URCU_CPUMASK_SIZE);
	if (ret <= 0)
		goto fallback;

	/* Parse the possible cpu mask, on failure fallback to sysconf. */
	ret = get_max_cpuid_from_mask((char *) &buf, ret);
	if (ret >= 0) {
		/* Add 1 to convert from max cpuid to an array len. */
		ret++;
		goto end;
	}

fallback:
	/* Fallback to sysconf. */
	ret = get_num_possible_cpus_fallback();

end:
	return ret;
}
#else
/*
 * On other platforms, only use sysconf.
 */
static inline int get_possible_cpus_array_len(void)
{
	return get_num_possible_cpus_sysconf();
}
#endif
Commit	Line	Data
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