sysdeps/unix/sysv/linux/sched_getcpu.c

   1 /* Copyright (C) 2007-2024 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <sched.h>
  20 #include <sysdep.h>
  21 #include <sysdep-vdso.h>
  22
  23 static int
  24 vsyscall_sched_getcpu (void)
  25 {
  26   unsigned int cpu;
  27   int r = -1;
  28 #ifdef HAVE_GETCPU_VSYSCALL
  29   r = INLINE_VSYSCALL (getcpu, 3, &cpu, NULL, NULL);
  30 #else
  31   r = INLINE_SYSCALL_CALL (getcpu, &cpu, NULL, NULL);
  32 #endif
  33   return r == -1 ? r : cpu;
  34 }
  35
  36 int
  37 sched_getcpu (void)
  38 {
  39   int cpu_id = THREAD_GETMEM_VOLATILE (THREAD_SELF, rseq_area.cpu_id);
  40   return __glibc_likely (cpu_id >= 0) ? cpu_id : vsyscall_sched_getcpu ();
  41 }