gdb/nat/linux-waitpid.c

   1 /* Wrapper implementation for waitpid for GNU/Linux (LWP layer).
   2
   3    Copyright (C) 2001-2014 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       va_end (args);
  44     }
  45 #else
  46   /* GDB-specific debugging output.  */
  47 #endif
  48 }
  49
  50 /* Wrapper function for waitpid which handles EINTR, and emulates
  51    __WALL for systems where that is not available.  */
  52
  53 int
  54 my_waitpid (int pid, int *status, int flags)
  55 {
  56   int ret, out_errno;
  57
  58   linux_debug ("my_waitpid (%d, 0x%x)\n", pid, flags);
  59
  60   if (flags & __WALL)
  61     {
  62       sigset_t block_mask, org_mask, wake_mask;
  63       int wnohang;
  64
  65       wnohang = (flags & WNOHANG) != 0;
  66       flags &= ~(__WALL | __WCLONE);
  67       flags |= WNOHANG;
  68
  69       /* Block all signals while here.  This avoids knowing about
  70          LinuxThread's signals.  */
  71       sigfillset (&block_mask);
  72       sigprocmask (SIG_BLOCK, &block_mask, &org_mask);
  73
  74       /* ... except during the sigsuspend below.  */
  75       sigemptyset (&wake_mask);
  76
  77       while (1)
  78         {
  79           /* Since all signals are blocked, there's no need to check
  80              for EINTR here.  */
  81           ret = waitpid (pid, status, flags);
  82           out_errno = errno;
  83
  84           if (ret == -1 && out_errno != ECHILD)
  85             break;
  86           else if (ret > 0)
  87             break;
  88
  89           if (flags & __WCLONE)
  90             {
  91               /* We've tried both flavors now.  If WNOHANG is set,
  92                  there's nothing else to do, just bail out.  */
  93               if (wnohang)
  94                 break;
  95
  96               linux_debug ("blocking\n");
  97
  98               /* Block waiting for signals.  */
  99               sigsuspend (&wake_mask);
 100             }
 101           flags ^= __WCLONE;
 102         }
 103
 104       sigprocmask (SIG_SETMASK, &org_mask, NULL);
 105     }
 106   else
 107     {
 108       do
 109         ret = waitpid (pid, status, flags);
 110       while (ret == -1 && errno == EINTR);
 111       out_errno = errno;
 112     }
 113
 114   linux_debug ("my_waitpid (%d, 0x%x): status(%x), %d\n",
 115                pid, flags, status ? *status : -1, ret);
 116
 117   errno = out_errno;
 118   return ret;
 119 }