misc: Add __get_nprocs_sched

This is an internal function meant to return the number of avaliable
processor where the process can scheduled, different than the
__get_nprocs which returns a the system available online CPU.

The Linux implementation currently only calls __get_nprocs(), which
in tuns calls sched_getaffinity.

Reviewed-by: Florian Weimer <fweimer@redhat.com>
(cherry picked from commit 11a02b035b)

include/sys/sysinfo.h

@@ -9,10 +9,15 @@
 extern int __get_nprocs_conf (void);
 libc_hidden_proto (__get_nprocs_conf)
 
-/* Return number of available processors.  */
+/* Return number of available processors (not all of them will be
+   available to the caller process).  */
 extern int __get_nprocs (void);
 libc_hidden_proto (__get_nprocs)
 
+/* Return the number of available processors which the process can
+   be scheduled.  */
+extern int __get_nprocs_sched (void) attribute_hidden;
+
 /* Return number of physical pages of memory in the system.  */
 extern long int __get_phys_pages (void);
 libc_hidden_proto (__get_phys_pages)

malloc/arena.c

@@ -879,7 +879,7 @@ arena_get2 (size_t size, mstate avoid_arena)
             narenas_limit = mp_.arena_max;
           else if (narenas > mp_.arena_test)
             {
-              int n = __get_nprocs ();
+              int n = __get_nprocs_sched ();
 
               if (n >= 1)
                 narenas_limit = NARENAS_FROM_NCORES (n);

misc/getsysstats.c

@@ -45,6 +45,12 @@ weak_alias (__get_nprocs, get_nprocs)
 link_warning (get_nprocs, "warning: get_nprocs will always return 1")
 
 
+int
+__get_nprocs_sched (void)
+{
+  return 1;
+}
+
 long int
 __get_phys_pages (void)
 {

sysdeps/mach/getsysstats.c

@@ -62,6 +62,12 @@ __get_nprocs (void)
 libc_hidden_def (__get_nprocs)
 weak_alias (__get_nprocs, get_nprocs)
 
+int
+__get_nprocs_sched (void)
+{
+  return __get_nprocs ();
+}
+
 /* Return the number of physical pages on the system. */
 long int
 __get_phys_pages (void)

sysdeps/unix/sysv/linux/getsysstats.c

@@ -88,6 +88,12 @@ __get_nprocs (void)
 libc_hidden_def (__get_nprocs)
 weak_alias (__get_nprocs, get_nprocs)
 
+int
+__get_nprocs_sched (void)
+{
+  return __get_nprocs ();
+}
+
 
 /* On some architectures it is possible to distinguish between configured
    and active cpus.  */