sched_setaffinity.c

glibc 库, 不仅可以学习使用库函数,还可以学习函数的具体实现,是提高功力的好资料

/* Copyright (C) 2002, 2003, 2004, 2005, 2007
   Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <errno.h>
#include <sched.h>
#include <string.h>
#include <sysdep.h>
#include <unistd.h>
#include <sys/types.h>
#include <shlib-compat.h>
#include <alloca.h>


#ifdef __NR_sched_setaffinity
static size_t __kernel_cpumask_size;


int
__sched_setaffinity_new (pid_t pid, size_t cpusetsize, const cpu_set_t *cpuset)
{
  if (__builtin_expect (__kernel_cpumask_size == 0, 0))
    {
      INTERNAL_SYSCALL_DECL (err);
      int res;

      size_t psize = 128;
      void *p = alloca (psize);

      while (res = INTERNAL_SYSCALL (sched_getaffinity, err, 3, getpid (),
				     psize, p),
	     INTERNAL_SYSCALL_ERROR_P (res, err)
	     && INTERNAL_SYSCALL_ERRNO (res, err) == EINVAL)
	p = extend_alloca (p, psize, 2 * psize);

      if (res == 0 || INTERNAL_SYSCALL_ERROR_P (res, err))
	{
	  __set_errno (INTERNAL_SYSCALL_ERRNO (res, err));
	  return -1;
	}

      __kernel_cpumask_size = res;
    }

  /* We now know the size of the kernel cpumask_t.  Make sure the user
     does not request to set a bit beyond that.  */
  for (size_t cnt = __kernel_cpumask_size; cnt < cpusetsize; ++cnt)
    if (((char *) cpuset)[cnt] != '\0')
      {
        /* Found a nonzero byte.  This means the user request cannot be
	   fulfilled.  */
	__set_errno (EINVAL);
	return -1;
      }

  int result = INLINE_SYSCALL (sched_setaffinity, 3, pid, cpusetsize, cpuset);

#ifdef RESET_VGETCPU_CACHE
  if (result != -1)
    RESET_VGETCPU_CACHE ();
#endif

  return result;
}
versioned_symbol (libc, __sched_setaffinity_new, sched_setaffinity,
		  GLIBC_2_3_4);


# if SHLIB_COMPAT (libc, GLIBC_2_3_3, GLIBC_2_3_4)
int
attribute_compat_text_section
__sched_setaffinity_old (pid_t pid, const cpu_set_t *cpuset)
{
  /* The old interface by default assumed a 1024 processor bitmap.  */
  return __sched_setaffinity_new (pid, 128, cpuset);
}
compat_symbol (libc, __sched_setaffinity_old, sched_setaffinity, GLIBC_2_3_3);
# endif
#else
# include <posix/sched_setaffinity.c>
#endif