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 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
  21 #include "includes.h"
  22
  23 /****************************************************************************
  24  Catch child exits and reap the child zombie status.
  25 ****************************************************************************/
  26
  27 static void sig_cld(int signum)
  28 {
  29         while (sys_waitpid((pid_t)-1,(int *)NULL, WNOHANG) > 0)
  30                 ;
  31
  32         /*
  33          * Turns out it's *really* important not to
  34          * restore the signal handler here if we have real POSIX
  35          * signal handling. If we do, then we get the signal re-delivered
  36          * immediately - hey presto - instant loop ! JRA.
  37          */
  38
  39 #if !defined(HAVE_SIGACTION)
  40         CatchSignal(SIGCLD, sig_cld);
  41 #endif
  42 }
  43
  44 /****************************************************************************
  45 catch child exits - leave status;
  46 ****************************************************************************/
  47
  48 static void sig_cld_leave_status(int signum)
  49 {
  50         /*
  51          * Turns out it's *really* important not to
  52          * restore the signal handler here if we have real POSIX
  53          * signal handling. If we do, then we get the signal re-delivered
  54          * immediately - hey presto - instant loop ! JRA.
  55          */
  56
  57 #if !defined(HAVE_SIGACTION)
  58         CatchSignal(SIGCLD, sig_cld_leave_status);
  59 #endif
  60 }
  61
  62 /*******************************************************************
  63  Block sigs.
  64 ********************************************************************/
  65
  66 void BlockSignals(bool block,int signum)
  67 {
  68 #ifdef HAVE_SIGPROCMASK
  69         sigset_t set;
  70         sigemptyset(&set);
  71         sigaddset(&set,signum);
  72         sigprocmask(block?SIG_BLOCK:SIG_UNBLOCK,&set,NULL);
  73 #elif defined(HAVE_SIGBLOCK)
  74         if (block) {
  75                 sigblock(sigmask(signum));
  76         } else {
  77                 sigsetmask(siggetmask() & ~sigmask(signum));
  78         }
  79 #else
  80         /* yikes! This platform can't block signals? */
  81         static int done;
  82         if (!done) {
  83                 DEBUG(0,("WARNING: No signal blocking available\n"));
  84                 done=1;
  85         }
  86 #endif
  87 }
  88
  89 /*******************************************************************
  90  Catch a signal. This should implement the following semantics:
  91
  92  1) The handler remains installed after being called.
  93  2) The signal should be blocked during handler execution.
  94 ********************************************************************/
  95
  96 void (*CatchSignal(int signum,void (*handler)(int )))(int)
  97 {
  98 #ifdef HAVE_SIGACTION
  99         struct sigaction act;
 100         struct sigaction oldact;
 101
 102         ZERO_STRUCT(act);
 103
 104         act.sa_handler = handler;
 105 #ifdef SA_RESTART
 106         /*
 107          * We *want* SIGALRM to interrupt a system call.
 108          */
 109         if(signum != SIGALRM)
 110                 act.sa_flags = SA_RESTART;
 111 #endif
 112         sigemptyset(&act.sa_mask);
 113         sigaddset(&act.sa_mask,signum);
 114         sigaction(signum,&act,&oldact);
 115         return oldact.sa_handler;
 116 #else /* !HAVE_SIGACTION */
 117         /* FIXME: need to handle sigvec and systems with broken signal() */
 118         return signal(signum, handler);
 119 #endif
 120 }
 121
 122 /*******************************************************************
 123  Ignore SIGCLD via whatever means is necessary for this OS.
 124 ********************************************************************/
 125
 126 void CatchChild(void)
 127 {
 128         CatchSignal(SIGCLD, sig_cld);
 129 }
 130
 131 /*******************************************************************
 132  Catch SIGCLD but leave the child around so it's status can be reaped.
 133 ********************************************************************/
 134
 135 void CatchChildLeaveStatus(void)
 136 {
 137         CatchSignal(SIGCLD, sig_cld_leave_status);
 138 }