lib/util/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 #include "system/wait.h"
  23
  24 /**
  25  * @file
  26  * @brief Signal handling
  27  */
  28
  29 /****************************************************************************
  30  Catch child exits and reap the child zombie status.
  31 ****************************************************************************/
  32
  33 static void sig_cld(int signum)
  34 {
  35         while (waitpid((pid_t)-1,(int *)NULL, WNOHANG) > 0)
  36                 ;
  37
  38         /*
  39          * Turns out it's *really* important not to
  40          * restore the signal handler here if we have real POSIX
  41          * signal handling. If we do, then we get the signal re-delivered
  42          * immediately - hey presto - instant loop ! JRA.
  43          */
  44
  45 #if !defined(HAVE_SIGACTION)
  46         CatchSignal(SIGCLD, sig_cld);
  47 #endif
  48 }
  49
  50 /****************************************************************************
  51 catch child exits - leave status;
  52 ****************************************************************************/
  53
  54 static void sig_cld_leave_status(int signum)
  55 {
  56         /*
  57          * Turns out it's *really* important not to
  58          * restore the signal handler here if we have real POSIX
  59          * signal handling. If we do, then we get the signal re-delivered
  60          * immediately - hey presto - instant loop ! JRA.
  61          */
  62
  63 #if !defined(HAVE_SIGACTION)
  64         CatchSignal(SIGCLD, sig_cld_leave_status);
  65 #endif
  66 }
  67
  68 /**
  69  Block sigs.
  70 **/
  71
  72 void BlockSignals(bool block, int signum)
  73 {
  74 #ifdef HAVE_SIGPROCMASK
  75         sigset_t set;
  76         sigemptyset(&set);
  77         sigaddset(&set,signum);
  78         sigprocmask(block?SIG_BLOCK:SIG_UNBLOCK,&set,NULL);
  79 #elif defined(HAVE_SIGBLOCK)
  80         if (block) {
  81                 sigblock(sigmask(signum));
  82         } else {
  83                 sigsetmask(siggetmask() & ~sigmask(signum));
  84         }
  85 #else
  86         /* yikes! This platform can't block signals? */
  87         static int done;
  88         if (!done) {
  89                 DEBUG(0,("WARNING: No signal blocking available\n"));
  90                 done=1;
  91         }
  92 #endif
  93 }
  94
  95 /**
  96  Catch a signal. This should implement the following semantics:
  97
  98  1) The handler remains installed after being called.
  99  2) The signal should be blocked during handler execution.
 100 **/
 101
 102 void (*CatchSignal(int signum,void (*handler)(int )))(int)
 103 {
 104 #ifdef HAVE_SIGACTION
 105         struct sigaction act;
 106         struct sigaction oldact;
 107
 108         ZERO_STRUCT(act);
 109
 110         act.sa_handler = handler;
 111 #ifdef SA_RESTART
 112         /*
 113          * We *want* SIGALRM to interrupt a system call.
 114          */
 115         if(signum != SIGALRM)
 116                 act.sa_flags = SA_RESTART;
 117 #endif
 118         sigemptyset(&act.sa_mask);
 119         sigaddset(&act.sa_mask,signum);
 120         sigaction(signum,&act,&oldact);
 121         return oldact.sa_handler;
 122 #else /* !HAVE_SIGACTION */
 123         /* FIXME: need to handle sigvec and systems with broken signal() */
 124         return signal(signum, handler);
 125 #endif
 126 }
 127
 128 /**
 129  Ignore SIGCLD via whatever means is necessary for this OS.
 130 **/
 131
 132 void CatchChild(void)
 133 {
 134         CatchSignal(SIGCLD, sig_cld);
 135 }
 136
 137 /**
 138  Catch SIGCLD but leave the child around so it's status can be reaped.
 139 **/
 140
 141 void CatchChildLeaveStatus(void)
 142 {
 143         CatchSignal(SIGCLD, sig_cld_leave_status);
 144 }