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Sourcecode: postgresql-8.4 version File versions

pqsignal.c

/*-------------------------------------------------------------------------
 *
 * pqsignal.c
 *      reliable BSD-style signal(2) routine stolen from RWW who stole it
 *      from Stevens...
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      $PostgreSQL: pgsql/src/backend/libpq/pqsignal.c,v 1.45 2009/01/01 17:23:42 momjian Exp $
 *
 * NOTES
 *          This shouldn't be in libpq, but the monitor and some other
 *          things need it...
 *
 *    A NOTE ABOUT SIGNAL HANDLING ACROSS THE VARIOUS PLATFORMS.
 *
 *    pg_config.h defines the macro HAVE_POSIX_SIGNALS for some platforms and
 *    not for others.  This file and pqsignal.h use that macro to decide
 *    how to handle signalling.
 *
 *    signal(2) handling - this is here because it affects some of
 *    the frontend commands as well as the backend server.
 *
 *    Ultrix and SunOS provide BSD signal(2) semantics by default.
 *
 *    SVID2 and POSIX signal(2) semantics differ from BSD signal(2)
 *    semantics.  We can use the POSIX sigaction(2) on systems that
 *    allow us to request restartable signals (SA_RESTART).
 *
 *    Some systems don't allow restartable signals at all unless we
 *    link to a special BSD library.
 *
 *    We devoutly hope that there aren't any systems that provide
 *    neither POSIX signals nor BSD signals.    The alternative
 *    is to do signal-handler reinstallation, which doesn't work well
 *    at all.
 * ------------------------------------------------------------------------*/

#include "postgres.h"

#include <signal.h>

#include "libpq/pqsignal.h"


#ifdef HAVE_SIGPROCMASK
sigset_t    UnBlockSig,
                  BlockSig,
                  AuthBlockSig;
#else
int               UnBlockSig,
                  BlockSig,
                  AuthBlockSig;
#endif


/*
 * Initialize BlockSig, UnBlockSig, and AuthBlockSig.
 *
 * BlockSig is the set of signals to block when we are trying to block
 * signals.  This includes all signals we normally expect to get, but NOT
 * signals that should never be turned off.
 *
 * AuthBlockSig is the set of signals to block during authentication;
 * it's essentially BlockSig minus SIGTERM, SIGQUIT, SIGALRM.
 *
 * UnBlockSig is the set of signals to block when we don't want to block
 * signals (is this ever nonzero??)
 */
void
pqinitmask(void)
{
#ifdef HAVE_SIGPROCMASK

      sigemptyset(&UnBlockSig);

      /* First set all signals, then clear some. */
      sigfillset(&BlockSig);
      sigfillset(&AuthBlockSig);

      /*
       * Unmark those signals that should never be blocked. Some of these signal
       * names don't exist on all platforms.  Most do, but might as well ifdef
       * them all for consistency...
       */
#ifdef SIGTRAP
      sigdelset(&BlockSig, SIGTRAP);
      sigdelset(&AuthBlockSig, SIGTRAP);
#endif
#ifdef SIGABRT
      sigdelset(&BlockSig, SIGABRT);
      sigdelset(&AuthBlockSig, SIGABRT);
#endif
#ifdef SIGILL
      sigdelset(&BlockSig, SIGILL);
      sigdelset(&AuthBlockSig, SIGILL);
#endif
#ifdef SIGFPE
      sigdelset(&BlockSig, SIGFPE);
      sigdelset(&AuthBlockSig, SIGFPE);
#endif
#ifdef SIGSEGV
      sigdelset(&BlockSig, SIGSEGV);
      sigdelset(&AuthBlockSig, SIGSEGV);
#endif
#ifdef SIGBUS
      sigdelset(&BlockSig, SIGBUS);
      sigdelset(&AuthBlockSig, SIGBUS);
#endif
#ifdef SIGSYS
      sigdelset(&BlockSig, SIGSYS);
      sigdelset(&AuthBlockSig, SIGSYS);
#endif
#ifdef SIGCONT
      sigdelset(&BlockSig, SIGCONT);
      sigdelset(&AuthBlockSig, SIGCONT);
#endif

/* Signals unique to Auth */
#ifdef SIGQUIT
      sigdelset(&AuthBlockSig, SIGQUIT);
#endif
#ifdef SIGTERM
      sigdelset(&AuthBlockSig, SIGTERM);
#endif
#ifdef SIGALRM
      sigdelset(&AuthBlockSig, SIGALRM);
#endif
#else
      /* Set the signals we want. */
      UnBlockSig = 0;
      BlockSig = sigmask(SIGQUIT) |
            sigmask(SIGTERM) | sigmask(SIGALRM) |
      /* common signals between two */
            sigmask(SIGHUP) |
            sigmask(SIGINT) | sigmask(SIGUSR1) |
            sigmask(SIGUSR2) | sigmask(SIGCHLD) |
            sigmask(SIGWINCH) | sigmask(SIGFPE);
      AuthBlockSig = sigmask(SIGHUP) |
            sigmask(SIGINT) | sigmask(SIGUSR1) |
            sigmask(SIGUSR2) | sigmask(SIGCHLD) |
            sigmask(SIGWINCH) | sigmask(SIGFPE);
#endif
}


/* Win32 signal handling is in backend/port/win32/signal.c */
#ifndef WIN32

/*
 * Set up a signal handler
 */
pqsigfunc
pqsignal(int signo, pqsigfunc func)
{
#if !defined(HAVE_POSIX_SIGNALS)
      return signal(signo, func);
#else
      struct sigaction act,
                        oact;

      act.sa_handler = func;
      sigemptyset(&act.sa_mask);
      act.sa_flags = 0;
      if (signo != SIGALRM)
            act.sa_flags |= SA_RESTART;
#ifdef SA_NOCLDSTOP
      if (signo == SIGCHLD)
            act.sa_flags |= SA_NOCLDSTOP;
#endif
      if (sigaction(signo, &act, &oact) < 0)
            return SIG_ERR;
      return oact.sa_handler;
#endif   /* !HAVE_POSIX_SIGNALS */
}

#endif   /* WIN32 */

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