gdb/nat/linux-waitpid.c

/* Wrapper implementation for waitpid for GNU/Linux (LWP layer).

   Copyright (C) 2001-2013 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#ifdef GDBSERVER
#include "server.h"
#else
#include "defs.h"
#include "signal.h"
#endif

#include "nat/linux-nat.h"
#include "nat/linux-waitpid.h"
#include "gdb_wait.h"

/* Print debugging output based on the format string FORMAT and
   its parameters.  */

static inline void
linux_debug (const char *format, ...)
{
#ifdef GDBSERVER
  if (debug_threads)
    {
      va_list args;
      va_start (args, format);
      vfprintf (stderr, format, args);
      fprintf (stderr, "\n");
      va_end (args);
    }
#else
  /* GDB-specific debugging output.  */
#endif
}

/* Wrapper function for waitpid which handles EINTR, and emulates
   __WALL for systems where that is not available.  */

int
my_waitpid (int pid, int *status, int flags)
{
  int ret, out_errno;

  linux_debug ("my_waitpid (%d, 0x%x)\n", pid, flags);

  if (flags & __WALL)
    {
      sigset_t block_mask, org_mask, wake_mask;
      int wnohang;

      wnohang = (flags & WNOHANG) != 0;
      flags &= ~(__WALL | __WCLONE);
      flags |= WNOHANG;

      /* Block all signals while here.  This avoids knowing about
	 LinuxThread's signals.  */
      sigfillset (&block_mask);
      sigprocmask (SIG_BLOCK, &block_mask, &org_mask);

      /* ... except during the sigsuspend below.  */
      sigemptyset (&wake_mask);

      while (1)
	{
	  /* Since all signals are blocked, there's no need to check
	     for EINTR here.  */
	  ret = waitpid (pid, status, flags);
	  out_errno = errno;

	  if (ret == -1 && out_errno != ECHILD)
	    break;
	  else if (ret > 0)
	    break;

	  if (flags & __WCLONE)
	    {
	      /* We've tried both flavors now.  If WNOHANG is set,
		 there's nothing else to do, just bail out.  */
	      if (wnohang)
		break;

	      linux_debug ("blocking\n");

	      /* Block waiting for signals.  */
	      sigsuspend (&wake_mask);
	    }
	  flags ^= __WCLONE;
	}

      sigprocmask (SIG_SETMASK, &org_mask, NULL);
    }
  else
    {
      do
	ret = waitpid (pid, status, flags);
      while (ret == -1 && errno == EINTR);
      out_errno = errno;
    }

  linux_debug ("my_waitpid (%d, 0x%x): status(%x), %d\n",
	       pid, flags, status ? *status : -1, ret);

  errno = out_errno;
  return ret;
}