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(__get_nprocs): Use /sys filesystem to determine which processors are online.

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This commit is contained in:
Ulrich Drepper 2007-07-31 22:43:57 +00:00
parent 558f030079
commit 58d43ba882
1 changed files with 51 additions and 1 deletions
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52
sysdeps/unix/sysv/linux/getsysstats.c
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@ -1,5 +1,5 @@
/* Determine various system internal values, Linux version.
Copyright (C) 1996-2001, 2002, 2003, 2006 Free Software Foundation, Inc.
Copyright (C) 1996-2001, 2002, 2003, 2006, 2007 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
@ -21,7 +21,9 @@
#include <alloca.h>
#include <assert.h>
#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <mntent.h>
#include <paths.h>
#include <stdio.h>
@ -32,6 +34,7 @@
#include <sys/sysinfo.h>
#include <atomic.h>
#include <not-cancel.h>
/* How we can determine the number of available processors depends on
@ -72,6 +75,53 @@ __get_nprocs ()
/* XXX Here will come a test for the new system call. */
/* Try to use the sysfs filesystem. It has actual information about
online processors. */
DIR *dir = __opendir ("/sys/devices/system/cpu");
if (dir != NULL)
{
int dfd = dirfd (dir);
int count = 0;
struct dirent64 *d;
while ((d = __readdir64 (dir)) != NULL)
/* NB: the sysfs has d_type support. */
if (d->d_type == DT_DIR && strncmp (d->d_name, "cpu", 3) == 0)
{
char *endp;
unsigned long int nr = strtoul (d->d_name + 3, &endp, 10);
if (nr != ULONG_MAX && endp != d->d_name + 3 && *endp == '\0')
{
/* Try reading the online file. */
char oname[_D_ALLOC_NAMLEN (d) + sizeof "/online"];
strcpy (stpcpy (oname, d->d_name), "/online");
/* We unconditionally use openat since the "online"
file became readable only after the openat system
call was introduced. */
char buf[1];
int fd = openat_not_cancel_3 (dfd, oname, O_RDONLY);
/* If we cannot read the online file we have to assume
the CPU is online. */
if (fd < 0)
++count;
else
{
if (read_not_cancel (fd, buf, sizeof (buf)) < 0
|| buf[0] == '1')
++count;
close_not_cancel_no_status (fd);
}
}
}
__closedir (dir);
return count;
}
/* The /proc/stat format is more uniform, use it by default. */
FILE *fp = fopen ("/proc/stat", "rc");
if (fp != NULL)