sigsuspend.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) 1996,1997,1998,1999,2000,2002,2003,2006
	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 <signal.h>
#include <unistd.h>

#include <sysdep-cancel.h>
#include <sys/syscall.h>
#include <bp-checks.h>

#include <kernel-features.h>


#if !__ASSUME_REALTIME_SIGNALS
/* The variable is shared between all wrappers around signal handling
   functions which have RT equivalents.  The definition is in sigaction.c.  */
extern int __libc_missing_rt_sigs;


static int
do_sigsuspend (const sigset_t *set)
{
# ifdef __NR_rt_sigsuspend
  /* First try the RT signals.  */
  if (!__libc_missing_rt_sigs)
    {
      /* XXX The size argument hopefully will have to be changed to the
	 real size of the user-level sigset_t.  */
      int saved_errno = errno;
      int result = INLINE_SYSCALL (rt_sigsuspend, 2,
				   CHECK_SIGSET (set), _NSIG / 8);
      if (result >= 0 || errno != ENOSYS)
	return result;

      __set_errno (saved_errno);
      __libc_missing_rt_sigs = 1;
    }
# endif

  return INLINE_SYSCALL (sigsuspend, 3, 0, 0, set->__val[0]);
}
#else
static inline int __attribute__ ((always_inline))
do_sigsuspend (const sigset_t *set)
{
  return INLINE_SYSCALL (rt_sigsuspend, 2, CHECK_SIGSET (set), _NSIG / 8);
}
#endif

/* Change the set of blocked signals to SET,
   wait until a signal arrives, and restore the set of blocked signals.  */
int
__sigsuspend (set)
     const sigset_t *set;
{
  if (SINGLE_THREAD_P)
    return do_sigsuspend (set);

  int oldtype = LIBC_CANCEL_ASYNC ();

  int result = do_sigsuspend (set);

  LIBC_CANCEL_RESET (oldtype);

  return result;
}
libc_hidden_def (__sigsuspend)
weak_alias (__sigsuspend, sigsuspend)
strong_alias (__sigsuspend, __libc_sigsuspend)

#ifndef NO_CANCELLATION
int
__sigsuspend_nocancel (set)
     const sigset_t *set;
{
  return do_sigsuspend (set);
}
#endif