source/lib/signal.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    signal handling functions
   4
   5    Copyright (C) Andrew Tridgell 1998
   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 2 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, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 #include "includes.h"
  23
  24 /****************************************************************************
  25  Catch child exits and reap the child zombie status.
  26 ****************************************************************************/
  27
  28 static void sig_cld(int signum)
  29 {
  30         while (sys_waitpid((pid_t)-1,(int *)NULL, WNOHANG) > 0)
  31                 ;
  32
  33         /*
  34          * Turns out it's *really* important not to
  35          * restore the signal handler here if we have real POSIX
  36          * signal handling. If we do, then we get the signal re-delivered
  37          * immediately - hey presto - instant loop ! JRA.
  38          */
  39
  40 #if !defined(HAVE_SIGACTION)
  41         CatchSignal(SIGCLD, sig_cld);
  42 #endif
  43 }
  44
  45 /****************************************************************************
  46 catch child exits - leave status;
  47 ****************************************************************************/
  48
  49 static void sig_cld_leave_status(int signum)
  50 {
  51         /*
  52          * Turns out it's *really* important not to
  53          * restore the signal handler here if we have real POSIX
  54          * signal handling. If we do, then we get the signal re-delivered
  55          * immediately - hey presto - instant loop ! JRA.
  56          */
  57
  58 #if !defined(HAVE_SIGACTION)
  59         CatchSignal(SIGCLD, sig_cld_leave_status);
  60 #else
  61         ;
  62 #endif
  63 }
  64
  65 /*******************************************************************
  66  Block sigs.
  67 ********************************************************************/
  68
  69 void BlockSignals(BOOL block,int signum)
  70 {
  71 #ifdef HAVE_SIGPROCMASK
  72         sigset_t set;
  73         sigemptyset(&set);
  74         sigaddset(&set,signum);
  75         sigprocmask(block?SIG_BLOCK:SIG_UNBLOCK,&set,NULL);
  76 #elif defined(HAVE_SIGBLOCK)
  77         if (block) {
  78                 sigblock(sigmask(signum));
  79         } else {
  80                 sigsetmask(siggetmask() & ~sigmask(signum));
  81         }
  82 #else
  83         /* yikes! This platform can't block signals? */
  84         static int done;
  85         if (!done) {
  86                 DEBUG(0,("WARNING: No signal blocking available\n"));
  87                 done=1;
  88         }
  89 #endif
  90 }
  91
  92 /*******************************************************************
  93  Catch a signal. This should implement the following semantics:
  94
  95  1) The handler remains installed after being called.
  96  2) The signal should be blocked during handler execution.
  97 ********************************************************************/
  98
  99 void (*CatchSignal(int signum,void (*handler)(int )))(int)
 100 {
 101 #ifdef HAVE_SIGACTION
 102         struct sigaction act;
 103         struct sigaction oldact;
 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,&oldact);
 118         return oldact.sa_handler;
 119 #else /* !HAVE_SIGACTION */
 120         /* FIXME: need to handle sigvec and systems with broken signal() */
 121         return signal(signum, handler);
 122 #endif
 123 }
 124
 125 /*******************************************************************
 126  Ignore SIGCLD via whatever means is necessary for this OS.
 127 ********************************************************************/
 128
 129 void CatchChild(void)
 130 {
 131         CatchSignal(SIGCLD, sig_cld);
 132 }
 133
 134 /*******************************************************************
 135  Catch SIGCLD but leave the child around so it's status can be reaped.
 136 ********************************************************************/
 137
 138 void CatchChildLeaveStatus(void)
 139 {
 140         CatchSignal(SIGCLD, sig_cld_leave_status);
 141 }