source/lib/signal.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 1.9.
   4    signal handling functions
   5
   6    Copyright (C) Andrew Tridgell 1998
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 #include "includes.h"
  24
  25 /****************************************************************************
  26  Catch child exits and reap the child zombie status.
  27 ****************************************************************************/
  28
  29 static void sig_cld(int signum)
  30 {
  31         while (sys_waitpid((pid_t)-1,(int *)NULL, WNOHANG) > 0)
  32                 ;
  33
  34         /*
  35          * Turns out it's *really* important not to
  36          * restore the signal handler here if we have real POSIX
  37          * signal handling. If we do, then we get the signal re-delivered
  38          * immediately - hey presto - instant loop ! JRA.
  39          */
  40
  41 #if !defined(HAVE_SIGACTION)
  42         CatchSignal(SIGCLD, sig_cld);
  43 #endif
  44 }
  45
  46 /****************************************************************************
  47 catch child exits - leave status;
  48 ****************************************************************************/
  49
  50 static void sig_cld_leave_status(int signum)
  51 {
  52         /*
  53          * Turns out it's *really* important not to
  54          * restore the signal handler here if we have real POSIX
  55          * signal handling. If we do, then we get the signal re-delivered
  56          * immediately - hey presto - instant loop ! JRA.
  57          */
  58
  59 #if !defined(HAVE_SIGACTION)
  60         CatchSignal(SIGCLD, sig_cld_leave_status);
  61 #else
  62         ;
  63 #endif
  64 }
  65
  66 /*******************************************************************
  67  Block sigs.
  68 ********************************************************************/
  69
  70 void BlockSignals(BOOL block,int signum)
  71 {
  72 #ifdef HAVE_SIGPROCMASK
  73         sigset_t set;
  74         sigemptyset(&set);
  75         sigaddset(&set,signum);
  76         sigprocmask(block?SIG_BLOCK:SIG_UNBLOCK,&set,NULL);
  77 #elif defined(HAVE_SIGBLOCK)
  78         if (block) {
  79                 sigblock(sigmask(signum));
  80         } else {
  81                 sigsetmask(siggetmask() & ~sigmask(signum));
  82         }
  83 #else
  84         /* yikes! This platform can't block signals? */
  85         static int done;
  86         if (!done) {
  87                 DEBUG(0,("WARNING: No signal blocking available\n"));
  88                 done=1;
  89         }
  90 #endif
  91 }
  92
  93 /*******************************************************************
  94  Catch a signal. This should implement the following semantics:
  95
  96  1) The handler remains installed after being called.
  97  2) The signal should be blocked during handler execution.
  98 ********************************************************************/
  99
 100 void CatchSignal(int signum,void (*handler)(int ))
 101 {
 102 #ifdef HAVE_SIGACTION
 103         struct sigaction act;
 104
 105         ZERO_STRUCT(act);
 106
 107         act.sa_handler = handler;
 108 #ifdef SA_RESTART
 109         /*
 110          * We *want* SIGALRM to interrupt a system call.
 111          */
 112         if(signum != SIGALRM)
 113                 act.sa_flags = SA_RESTART;
 114 #endif
 115         sigemptyset(&act.sa_mask);
 116         sigaddset(&act.sa_mask,signum);
 117         sigaction(signum,&act,NULL);
 118 #else /* !HAVE_SIGACTION */
 119         /* FIXME: need to handle sigvec and systems with broken signal() */
 120         signal(signum, handler);
 121 #endif
 122 }
 123
 124 /*******************************************************************
 125  Ignore SIGCLD via whatever means is necessary for this OS.
 126 ********************************************************************/
 127
 128 void CatchChild(void)
 129 {
 130         CatchSignal(SIGCLD, sig_cld);
 131 }
 132
 133 /*******************************************************************
 134  Catch SIGCLD but leave the child around so it's status can be reaped.
 135 ********************************************************************/
 136
 137 void CatchChildLeaveStatus(void)
 138 {
 139         CatchSignal(SIGCLD, sig_cld_leave_status);
 140 }