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 #endif
  61 }
  62
  63 /*******************************************************************
  64  Block sigs.
  65 ********************************************************************/
  66
  67 void BlockSignals(BOOL block,int signum)
  68 {
  69 #ifdef HAVE_SIGPROCMASK
  70         sigset_t set;
  71         sigemptyset(&set);
  72         sigaddset(&set,signum);
  73         sigprocmask(block?SIG_BLOCK:SIG_UNBLOCK,&set,NULL);
  74 #elif defined(HAVE_SIGBLOCK)
  75         if (block) {
  76                 sigblock(sigmask(signum));
  77         } else {
  78                 sigsetmask(siggetmask() & ~sigmask(signum));
  79         }
  80 #else
  81         /* yikes! This platform can't block signals? */
  82         static int done;
  83         if (!done) {
  84                 DEBUG(0,("WARNING: No signal blocking available\n"));
  85                 done=1;
  86         }
  87 #endif
  88 }
  89
  90 /*******************************************************************
  91  Catch a signal. This should implement the following semantics:
  92
  93  1) The handler remains installed after being called.
  94  2) The signal should be blocked during handler execution.
  95 ********************************************************************/
  96
  97 void (*CatchSignal(int signum,void (*handler)(int )))(int)
  98 {
  99 #ifdef HAVE_SIGACTION
 100         struct sigaction act;
 101         struct sigaction oldact;
 102
 103         ZERO_STRUCT(act);
 104
 105         act.sa_handler = handler;
 106 #ifdef SA_RESTART
 107         /*
 108          * We *want* SIGALRM to interrupt a system call.
 109          */
 110         if(signum != SIGALRM)
 111                 act.sa_flags = SA_RESTART;
 112 #endif
 113         sigemptyset(&act.sa_mask);
 114         sigaddset(&act.sa_mask,signum);
 115         sigaction(signum,&act,&oldact);
 116         return oldact.sa_handler;
 117 #else /* !HAVE_SIGACTION */
 118         /* FIXME: need to handle sigvec and systems with broken signal() */
 119         return signal(signum, handler);
 120 #endif
 121 }
 122
 123 /*******************************************************************
 124  Ignore SIGCLD via whatever means is necessary for this OS.
 125 ********************************************************************/
 126
 127 void CatchChild(void)
 128 {
 129         CatchSignal(SIGCLD, sig_cld);
 130 }
 131
 132 /*******************************************************************
 133  Catch SIGCLD but leave the child around so it's status can be reaped.
 134 ********************************************************************/
 135
 136 void CatchChildLeaveStatus(void)
 137 {
 138         CatchSignal(SIGCLD, sig_cld_leave_status);
 139 }