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 "replace.h"
  22 #include "system/wait.h"
  23 #include "debug.h"
  24 #include "lib/util/signal.h" /* Avoid /usr/include/signal.h */
  25
  26 /**
  27  * @file
  28  * @brief Signal handling
  29  */
  30
  31 /****************************************************************************
  32  Catch child exits and reap the child zombie status.
  33 ****************************************************************************/
  34
  35 static void sig_cld(int signum)
  36 {
  37         while (waitpid((pid_t)-1,(int *)NULL, WNOHANG) > 0)
  38                 ;
  39
  40         /*
  41          * Turns out it's *really* important not to
  42          * restore the signal handler here if we have real POSIX
  43          * signal handling. If we do, then we get the signal re-delivered
  44          * immediately - hey presto - instant loop ! JRA.
  45          */
  46
  47 #if !defined(HAVE_SIGACTION)
  48         CatchSignal(SIGCLD, sig_cld);
  49 #endif
  50 }
  51
  52 /****************************************************************************
  53 catch child exits - leave status;
  54 ****************************************************************************/
  55
  56 static void sig_cld_leave_status(int signum)
  57 {
  58         /*
  59          * Turns out it's *really* important not to
  60          * restore the signal handler here if we have real POSIX
  61          * signal handling. If we do, then we get the signal re-delivered
  62          * immediately - hey presto - instant loop ! JRA.
  63          */
  64
  65 #if !defined(HAVE_SIGACTION)
  66         CatchSignal(SIGCLD, sig_cld_leave_status);
  67 #endif
  68 }
  69
  70 /**
  71  Block sigs.
  72 **/
  73
  74 void BlockSignals(bool block, int signum)
  75 {
  76 #ifdef HAVE_SIGPROCMASK
  77         sigset_t set;
  78         sigemptyset(&set);
  79         sigaddset(&set,signum);
  80         sigprocmask(block?SIG_BLOCK:SIG_UNBLOCK,&set,NULL);
  81 #elif defined(HAVE_SIGBLOCK)
  82         if (block) {
  83                 sigblock(sigmask(signum));
  84         } else {
  85                 sigsetmask(siggetmask() & ~sigmask(signum));
  86         }
  87 #else
  88         /* yikes! This platform can't block signals? */
  89         static int done;
  90         if (!done) {
  91                 DEBUG(0,("WARNING: No signal blocking available\n"));
  92                 done=1;
  93         }
  94 #endif
  95 }
  96
  97 /**
  98  Catch a signal. This should implement the following semantics:
  99
 100  1) The handler remains installed after being called.
 101  2) The signal should be blocked during handler execution.
 102 **/
 103
 104 void (*CatchSignal(int signum,void (*handler)(int )))(int)
 105 {
 106 #ifdef HAVE_SIGACTION
 107         struct sigaction act;
 108         struct sigaction oldact;
 109
 110         ZERO_STRUCT(act);
 111
 112         act.sa_handler = handler;
 113 #ifdef SA_RESTART
 114         /*
 115          * We *want* SIGALRM to interrupt a system call.
 116          */
 117         if(signum != SIGALRM)
 118                 act.sa_flags = SA_RESTART;
 119 #endif
 120         sigemptyset(&act.sa_mask);
 121         sigaddset(&act.sa_mask,signum);
 122         sigaction(signum,&act,&oldact);
 123         return oldact.sa_handler;
 124 #else /* !HAVE_SIGACTION */
 125         /* FIXME: need to handle sigvec and systems with broken signal() */
 126         return signal(signum, handler);
 127 #endif
 128 }
 129
 130 /**
 131  Ignore SIGCLD via whatever means is necessary for this OS.
 132 **/
 133
 134 void (*CatchChild(void))(int)
 135 {
 136         return CatchSignal(SIGCLD, sig_cld);
 137 }
 138
 139 /**
 140  Catch SIGCLD but leave the child around so it's status can be reaped.
 141 **/
 142
 143 void (*CatchChildLeaveStatus(void))(int)
 144 {
 145         return CatchSignal(SIGCLD, sig_cld_leave_status);
 146 }