gdb/nat/linux-waitpid.c

   1 /* Wrapper implementation for waitpid for GNU/Linux (LWP layer).
   2
   3    Copyright (C) 2001-2013 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifdef GDBSERVER
  21 #include "server.h"
  22 #else
  23 #include "defs.h"
  24 #include "signal.h"
  25 #endif
  26
  27 #include "nat/linux-nat.h"
  28 #include "nat/linux-waitpid.h"
  29 #include "gdb_wait.h"
  30
  31 /* Print debugging output based on the format string FORMAT and
  32    its parameters.  */
  33
  34 static inline void
  35 linux_debug (const char *format, ...)
  36 {
  37 #ifdef GDBSERVER
  38   if (debug_threads)
  39     {
  40       va_list args;
  41       va_start (args, format);
  42       vfprintf (stderr, format, args);
  43       fprintf (stderr, "\n");
  44       va_end (args);
  45     }
  46 #else
  47   /* GDB-specific debugging output.  */
  48 #endif
  49 }
  50
  51 /* Wrapper function for waitpid which handles EINTR, and emulates
  52    __WALL for systems where that is not available.  */
  53
  54 int
  55 my_waitpid (int pid, int *status, int flags)
  56 {
  57   int ret, out_errno;
  58
  59   linux_debug ("my_waitpid (%d, 0x%x)\n", pid, flags);
  60
  61   if (flags & __WALL)
  62     {
  63       sigset_t block_mask, org_mask, wake_mask;
  64       int wnohang;
  65
  66       wnohang = (flags & WNOHANG) != 0;
  67       flags &= ~(__WALL | __WCLONE);
  68       flags |= WNOHANG;
  69
  70       /* Block all signals while here.  This avoids knowing about
  71          LinuxThread's signals.  */
  72       sigfillset (&block_mask);
  73       sigprocmask (SIG_BLOCK, &block_mask, &org_mask);
  74
  75       /* ... except during the sigsuspend below.  */
  76       sigemptyset (&wake_mask);
  77
  78       while (1)
  79         {
  80           /* Since all signals are blocked, there's no need to check
  81              for EINTR here.  */
  82           ret = waitpid (pid, status, flags);
  83           out_errno = errno;
  84
  85           if (ret == -1 && out_errno != ECHILD)
  86             break;
  87           else if (ret > 0)
  88             break;
  89
  90           if (flags & __WCLONE)
  91             {
  92               /* We've tried both flavors now.  If WNOHANG is set,
  93                  there's nothing else to do, just bail out.  */
  94               if (wnohang)
  95                 break;
  96
  97               linux_debug ("blocking\n");
  98
  99               /* Block waiting for signals.  */
 100               sigsuspend (&wake_mask);
 101             }
 102           flags ^= __WCLONE;
 103         }
 104
 105       sigprocmask (SIG_SETMASK, &org_mask, NULL);
 106     }
 107   else
 108     {
 109       do
 110         ret = waitpid (pid, status, flags);
 111       while (ret == -1 && errno == EINTR);
 112       out_errno = errno;
 113     }
 114
 115   linux_debug ("my_waitpid (%d, 0x%x): status(%x), %d\n",
 116                pid, flags, status ? *status : -1, ret);
 117
 118   errno = out_errno;
 119   return ret;
 120 }