*/
#define _LGPL_SOURCE
+#include <assert.h>
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
#include <unistd.h>
#include <pthread.h>
+#include <stdlib.h>
#include <urcu/compiler.h>
+#include "common/align.h"
+#include "common/logging.h"
#include "common/smp.h"
static int num_possible_cpus_cache;
#if (defined(__GLIBC__) || defined( __UCLIBC__))
-static void _get_num_possible_cpus(void)
+int get_num_possible_cpus_fallback(void)
{
- int result;
-
/* On Linux, when some processors are offline
* _SC_NPROCESSORS_CONF counts the offline
* processors, whereas _SC_NPROCESSORS_ONLN
* this sysconf, in which case the arrays
* indexed by processor would overflow.
*/
- result = sysconf(_SC_NPROCESSORS_CONF);
- if (result == -1)
- return;
- num_possible_cpus_cache = result;
+ return sysconf(_SC_NPROCESSORS_CONF);
}
#else
#define __max(a,b) ((a)>(b)?(a):(b))
-static void _get_num_possible_cpus(void)
+int get_num_possible_cpus_fallback(void)
{
- int result, count = 0;
+ int count = 0;
DIR *cpudir;
struct dirent *entry;
/*
* Get the sysconf value as a fallback. Keep the highest number.
*/
- result = __max(sysconf(_SC_NPROCESSORS_CONF), count);
+ return __max(sysconf(_SC_NPROCESSORS_CONF), count);
+}
+#endif
+
+/*
+ * 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.
+ */
+int get_possible_cpu_mask_from_sysfs(char *buf, size_t max_bytes)
+{
+ ssize_t bytes_read = 0;
+ size_t total_bytes_read = 0;
+ int fd = 0;
+
+ if (buf == NULL)
+ return -1;
+
+ fd = open("/sys/devices/system/cpu/possible", O_RDONLY);
+ if (fd < 0)
+ return -1;
+
+ 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 {
+ return -1;
+ }
+ }
+
+ total_bytes_read += bytes_read;
+ assert(total_bytes_read <= max_bytes);
+ } while (max_bytes > total_bytes_read && bytes_read > 0);
+
+ if (close(fd))
+ PERROR("close");
+
+ /*
+ * 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';
+
+ return total_bytes_read;
+}
+
+/*
+ * Get the number of CPUs from the possible cpu mask.
+ *
+ * pmask: the mask to parse.
+ * len: the len of the mask excluding '\0'.
+ *
+ * Returns the number of possible CPUs from the mask or 0 on error.
+ */
+int get_num_possible_cpus_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 both methods failed, don't store the value.
+ * If we read a CPU index, increment it by one to return a number of
+ * CPUs.
*/
- if (result < 1)
+ if ((&pmask[i] != endptr) && (cpu_index < INT_MAX))
+ return (int) cpu_index + 1;
+
+error:
+ return 0;
+}
+
+static void _get_num_possible_cpus(void)
+{
+ int ret;
+ int buf_len = LTTNG_UST_PAGE_SIZE;
+ char buf[buf_len];
+
+ /* Get the possible cpu mask from sysfs, fallback to sysconf. */
+ ret = get_possible_cpu_mask_from_sysfs((char *) &buf, buf_len);
+ if (ret <= 0)
+ goto fallback;
+
+ /* Parse the possible cpu mask, on failure fallback to sysconf. */
+ ret = get_num_possible_cpus_from_mask((char *) &buf, ret);
+ if (ret > 0)
+ goto end;
+
+fallback:
+ /* Fallback to sysconf. */
+ ret = get_num_possible_cpus_fallback();
+
+end:
+ /* If all methods failed, don't store the value. */
+ if (ret < 1)
return;
- num_possible_cpus_cache = result;
+
+ num_possible_cpus_cache = ret;
}
-#endif
/*
* Returns the total number of CPUs in the system. If the cache is not yet
- * initialized, get the value from the system through sysconf and cache it.
+ * initialized, get the value from "/sys/devices/system/cpu/possible" or
+ * fallback to sysconf and cache it.
*
- * If the sysconf call fails, don't populate the cache and return 0.
+ * If all methods fail, don't populate the cache and return 0.
*/
int num_possible_cpus(void)
{
projects / lttng-ust.git / blobdiff