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linux: Use /sys/devices/system/cpu on __get_nprocs_conf (BZ#28991) 

Currently on Linux __get_nprocs_conf first tries to enumerate the
cpus present in the system by iterating on /sys/devices/system/cpuX
directories.  This only enumerates the CPUs that are present in
system (but possibly offline), not taking in account possible CPU
that might added in the system through hotplugging.

Linux provides the maximum number of configured cpus on the
/sys/devices/system/cpu file.  Although it might present a larger
value of possible active CPUs on some system (where kernel either
get the information from firmaware or is configured at boot time),
the information is what kernel presents to userland.

This also change the returned value of _SC_NPROCESSORS_CONF, which
aligns as the maximum configure cpu in the system.

Checked on x86_64-linux-gnu.

Reviewed-by: Florian Weimer <fweimer@redhat.com>
This commit is contained in:
Adhemerval Zanella 2022-03-23 17:29:03 -03:00
parent f787e138aa
commit 97a912f7a8
1 changed files with 4 additions and 32 deletions
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36
sysdeps/unix/sysv/linux/getsysstats.c
View File

@ -19,7 +19,6 @@
#include <array_length.h>
#include <assert.h>
#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <ldsodefs.h>
#include <limits.h>
@ -136,7 +135,7 @@ get_nproc_stat (void)
}
static int
get_nprocs_cpu_online (void)
read_sysfs_file (const char *fname)
{
enum { buffer_size = 1024 };
char buffer[buffer_size];
@ -146,7 +145,7 @@ get_nprocs_cpu_online (void)
const int flags = O_RDONLY | O_CLOEXEC;
/* This file contains comma-separated ranges. */
int fd = __open_nocancel ("/sys/devices/system/cpu/online", flags);
int fd = __open_nocancel (fname, flags);
char *l;
int result = 0;
if (fd != -1)
@ -190,31 +189,6 @@ get_nprocs_cpu_online (void)
return result;
}
static int
get_nprocs_cpu (void)
{
int count = 0;
DIR *dir = __opendir ("/sys/devices/system/cpu");
if (dir != NULL)
{
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')
++count;
}
__closedir (dir);
}
return count;
}
static int
get_nprocs_fallback (void)
{
@ -239,8 +213,7 @@ get_nprocs_fallback (void)
int
__get_nprocs (void)
{
/* Try /sys/devices/system/cpu/online first. */
int result = get_nprocs_cpu_online ();
int result = read_sysfs_file ("/sys/devices/system/cpu/online");
if (result != 0)
return result;
@ -255,8 +228,7 @@ weak_alias (__get_nprocs, get_nprocs)
int
__get_nprocs_conf (void)
{
/* Try /sys/devices/system/cpu/ first. */
int result = get_nprocs_cpu ();
int result = read_sysfs_file ("/sys/devices/system/cpu/possible");
if (result != 0)
return result;