Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * pqsignal.c
       4             :  *    Backend signal(2) support (see also src/port/pqsignal.c)
       5             :  *
       6             :  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  *
      10             :  * IDENTIFICATION
      11             :  *    src/backend/libpq/pqsignal.c
      12             :  *
      13             :  * ------------------------------------------------------------------------
      14             :  */
      15             : 
      16             : #include "postgres.h"
      17             : 
      18             : #include "libpq/pqsignal.h"
      19             : 
      20             : 
      21             : /* Global variables */
      22             : sigset_t    UnBlockSig,
      23             :             BlockSig,
      24             :             StartupBlockSig;
      25             : 
      26             : 
      27             : /*
      28             :  * Initialize BlockSig, UnBlockSig, and StartupBlockSig.
      29             :  *
      30             :  * BlockSig is the set of signals to block when we are trying to block
      31             :  * signals.  This includes all signals we normally expect to get, but NOT
      32             :  * signals that should never be turned off.
      33             :  *
      34             :  * StartupBlockSig is the set of signals to block during startup packet
      35             :  * collection; it's essentially BlockSig minus SIGTERM, SIGQUIT, SIGALRM.
      36             :  *
      37             :  * UnBlockSig is the set of signals to block when we don't want to block
      38             :  * signals (is this ever nonzero??)
      39             :  */
      40             : void
      41        2440 : pqinitmask(void)
      42             : {
      43        2440 :     sigemptyset(&UnBlockSig);
      44             : 
      45             :     /* First set all signals, then clear some. */
      46        2440 :     sigfillset(&BlockSig);
      47        2440 :     sigfillset(&StartupBlockSig);
      48             : 
      49             :     /*
      50             :      * Unmark those signals that should never be blocked. Some of these signal
      51             :      * names don't exist on all platforms.  Most do, but might as well ifdef
      52             :      * them all for consistency...
      53             :      */
      54             : #ifdef SIGTRAP
      55        2440 :     sigdelset(&BlockSig, SIGTRAP);
      56        2440 :     sigdelset(&StartupBlockSig, SIGTRAP);
      57             : #endif
      58             : #ifdef SIGABRT
      59        2440 :     sigdelset(&BlockSig, SIGABRT);
      60        2440 :     sigdelset(&StartupBlockSig, SIGABRT);
      61             : #endif
      62             : #ifdef SIGILL
      63        2440 :     sigdelset(&BlockSig, SIGILL);
      64        2440 :     sigdelset(&StartupBlockSig, SIGILL);
      65             : #endif
      66             : #ifdef SIGFPE
      67        2440 :     sigdelset(&BlockSig, SIGFPE);
      68        2440 :     sigdelset(&StartupBlockSig, SIGFPE);
      69             : #endif
      70             : #ifdef SIGSEGV
      71        2440 :     sigdelset(&BlockSig, SIGSEGV);
      72        2440 :     sigdelset(&StartupBlockSig, SIGSEGV);
      73             : #endif
      74             : #ifdef SIGBUS
      75        2440 :     sigdelset(&BlockSig, SIGBUS);
      76        2440 :     sigdelset(&StartupBlockSig, SIGBUS);
      77             : #endif
      78             : #ifdef SIGSYS
      79        2440 :     sigdelset(&BlockSig, SIGSYS);
      80        2440 :     sigdelset(&StartupBlockSig, SIGSYS);
      81             : #endif
      82             : #ifdef SIGCONT
      83        2440 :     sigdelset(&BlockSig, SIGCONT);
      84        2440 :     sigdelset(&StartupBlockSig, SIGCONT);
      85             : #endif
      86             : 
      87             : /* Signals unique to startup */
      88             : #ifdef SIGQUIT
      89        2440 :     sigdelset(&StartupBlockSig, SIGQUIT);
      90             : #endif
      91             : #ifdef SIGTERM
      92        2440 :     sigdelset(&StartupBlockSig, SIGTERM);
      93             : #endif
      94             : #ifdef SIGALRM
      95        2440 :     sigdelset(&StartupBlockSig, SIGALRM);
      96             : #endif
      97        2440 : }
      98             : 
      99             : /*
     100             :  * Set up a postmaster signal handler for signal "signo"
     101             :  *
     102             :  * Returns the previous handler.
     103             :  *
     104             :  * This is used only in the postmaster, which has its own odd approach to
     105             :  * signal handling.  For signals with handlers, we block all signals for the
     106             :  * duration of signal handler execution.  We also do not set the SA_RESTART
     107             :  * flag; this should be safe given the tiny range of code in which the
     108             :  * postmaster ever unblocks signals.
     109             :  *
     110             :  * pqinitmask() must have been invoked previously.
     111             :  *
     112             :  * On Windows, this function is just an alias for pqsignal()
     113             :  * (and note that it's calling the code in src/backend/port/win32/signal.c,
     114             :  * not src/port/pqsignal.c).  On that platform, the postmaster's signal
     115             :  * handlers still have to block signals for themselves.
     116             :  */
     117             : pqsigfunc
     118        9624 : pqsignal_pm(int signo, pqsigfunc func)
     119             : {
     120             : #ifndef WIN32
     121             :     struct sigaction act,
     122             :                 oact;
     123             : 
     124        9624 :     act.sa_handler = func;
     125        9624 :     if (func == SIG_IGN || func == SIG_DFL)
     126             :     {
     127             :         /* in these cases, act the same as pqsignal() */
     128        4010 :         sigemptyset(&act.sa_mask);
     129        4010 :         act.sa_flags = SA_RESTART;
     130             :     }
     131             :     else
     132             :     {
     133        5614 :         act.sa_mask = BlockSig;
     134        5614 :         act.sa_flags = 0;
     135             :     }
     136             : #ifdef SA_NOCLDSTOP
     137        9624 :     if (signo == SIGCHLD)
     138         802 :         act.sa_flags |= SA_NOCLDSTOP;
     139             : #endif
     140        9624 :     if (sigaction(signo, &act, &oact) < 0)
     141           0 :         return SIG_ERR;
     142        9624 :     return oact.sa_handler;
     143             : #else                           /* WIN32 */
     144             :     return pqsignal(signo, func);
     145             : #endif
     146             : }