source4/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 #include "system/wait.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 #endif
  62 }
  63
  64 /*******************************************************************
  65  Block sigs.
  66 ********************************************************************/
  67
  68 void BlockSignals(BOOL block,int signum)
  69 {
  70 #ifdef HAVE_SIGPROCMASK
  71         sigset_t set;
  72         sigemptyset(&set);
  73         sigaddset(&set,signum);
  74         sigprocmask(block?SIG_BLOCK:SIG_UNBLOCK,&set,NULL);
  75 #elif defined(HAVE_SIGBLOCK)
  76         if (block) {
  77                 sigblock(sigmask(signum));
  78         } else {
  79                 sigsetmask(siggetmask() & ~sigmask(signum));
  80         }
  81 #else
  82         /* yikes! This platform can't block signals? */
  83         static int done;
  84         if (!done) {
  85                 DEBUG(0,("WARNING: No signal blocking available\n"));
  86                 done=1;
  87         }
  88 #endif
  89 }
  90
  91 /*******************************************************************
  92  Catch a signal. This should implement the following semantics:
  93
  94  1) The handler remains installed after being called.
  95  2) The signal should be blocked during handler execution.
  96 ********************************************************************/
  97
  98 void (*CatchSignal(int signum,void (*handler)(int )))(int)
  99 {
 100 #ifdef HAVE_SIGACTION
 101         struct sigaction act;
 102         struct sigaction oldact;
 103
 104         ZERO_STRUCT(act);
 105
 106         act.sa_handler = handler;
 107 #ifdef SA_RESTART
 108         /*
 109          * We *want* SIGALRM to interrupt a system call.
 110          */
 111         if(signum != SIGALRM)
 112                 act.sa_flags = SA_RESTART;
 113 #endif
 114         sigemptyset(&act.sa_mask);
 115         sigaddset(&act.sa_mask,signum);
 116         sigaction(signum,&act,&oldact);
 117         return oldact.sa_handler;
 118 #else /* !HAVE_SIGACTION */
 119         /* FIXME: need to handle sigvec and systems with broken signal() */
 120         return 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 }