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Unix/Linux 网络时间协议版本3 Network Time Protocol Version 3 (NTP) distribution for Unix systems

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From: Don Lewis <[e-mail]>
Message-Id: <[e-mail]>
Date: Tue, 11 Feb 1997 02:33:07 -0800
In-Reply-To: [e-mail]
       "Re: xntpd ntp_io.c input_handler reentered unsafely" (Feb 11,  3:07am)
X-Mailer: Mail User's Shell (7.2.6 alpha(3) 7/19/95)
To: [e-mail]
Subject: Re: xntpd ntp_io.c input_handler reentered unsafely
Cc: [e-mail]

I studied the code some more, and it has to keep the signal handler
rather than reset it to SIG_DFL.  Otherwise the SIGALRM handler would
only work once.

} If you have any suggestions or patches on how to handle things with
} xntpd, I'd be happy to receive them.
} 
} 5.89.5 is already out, and there might be another release due out soon
} with some more small changes to input_handler in ntp_io.c .

Here's a patch vs. 5.89.5.  The changes are:

	configure.in to looks for sigvec()

	matching change to config.h.in

	libntp/syssignal.c changed to use the appropriate signal
	implementation

	bogus call to sigset() in sigio_handler() removed

	sigio handler saves and restores errno, otherwise
	errno could be corrupted outside the signal context

	set_signal() always just calls signal_no_reset(),
	the mask twiddling stuff in the sigaction() version
	was redundant

	save and restore errno in the debug signal handlers in
	xntpd/ntpd.c 

Not changed:

	configure isn't any smarter about HAVE_SIGNALED_IO

	reentrant calls to msyslog() are possible since it is
	called from within the signal handlers and from the part
	of the loop in worker_thread where signals are not blocked
	(the debug signals aren't blocked at all).  Core dumps could
	result ...

These changes at at least compile under Solaris 2.5.1 and SunOS 4.1.4 ...

*** ORIGconfig.h.in	Wed Feb  5 00:04:51 1997
--- config.h.in	Tue Feb 11 01:38:16 1997
***************
*** 462,467 ****
--- 462,470 ----
  /* Define if you have the sigaction function.  */
  #undef HAVE_SIGACTION
  
+ /* Define if you have the sigvec function.  */
+ #undef HAVE_SIGVEC
+ 
  /* Define if you have the sigset function.  */
  #undef HAVE_SIGSET
  
*** ORIGconfigure.in	Mon Feb 10 17:27:27 1997
--- configure.in	Tue Feb 11 01:02:37 1997
***************
*** 284,290 ****
  AC_CHECK_FUNCS(gettimeofday getuid K_open kvm_open memcpy memmove memset nice)
  AC_CHECK_FUNCS(nlist ntp_adjtime ntp_gettime plock pututline pututxline rtprio)
  AC_CHECK_FUNCS(setlinebuf setpgid setpriority setsid settimeofday setvbuf)
! AC_CHECK_FUNCS(sigaction sigset sigsuspend stime strchr sysconf uname updwtmp)
  AC_CHECK_FUNCS(updwtmpx vsprintf)
  
  AC_CACHE_CHECK(number of arguments to gettimeofday(), ac_cv_func_Xettimeofday_nargs,
--- 284,290 ----
  AC_CHECK_FUNCS(gettimeofday getuid K_open kvm_open memcpy memmove memset nice)
  AC_CHECK_FUNCS(nlist ntp_adjtime ntp_gettime plock pututline pututxline rtprio)
  AC_CHECK_FUNCS(setlinebuf setpgid setpriority setsid settimeofday setvbuf)
! AC_CHECK_FUNCS(sigaction sigvec sigset sigsuspend stime strchr sysconf uname updwtmp)
  AC_CHECK_FUNCS(updwtmpx vsprintf)
  
  AC_CACHE_CHECK(number of arguments to gettimeofday(), ac_cv_func_Xettimeofday_nargs,
*** libntp/ORIGsyssignal.c	Sat Feb  1 00:47:37 1997
--- libntp/syssignal.c	Tue Feb 11 01:37:20 1997
***************
*** 47,60 ****
      }
  }
  
! #else  /* not HAVE_SIGACTION */
  
! RETSIGTYPE
  signal_no_reset(sig, func)
  int sig;
  RETSIGTYPE (*func) P((int));
  {
!     signal(sig, func);
  }
- #endif /* not HAVE_SIGACTION */
  
--- 47,102 ----
      }
  }
  
! #elif  HAVE_SIGVEC
  
! void
  signal_no_reset(sig, func)
  int sig;
  RETSIGTYPE (*func) P((int));
  {
!     struct sigvec sv;
!     int n;
! 
!     bzero((char *) &sv, sizeof(sv));
!     sv.sv_handler = func;
!     n = sigvec(sig, &sv, (struct sigvec *)NULL);
!     if (n == -1) {
! 	perror("sigvec");
!         exit(1);
!     }
  }
  
+ #elif  HAVE_SIGSET
+ 
+ void
+ signal_no_reset(sig, func)
+ int sig;
+ RETSIGTYPE (*func) P((int));
+ {
+     int n;
+ 
+     n = sigset(sig, func);
+     if (n == -1) {
+ 	perror("sigset");
+         exit(1);
+     }
+ }
+ 
+ #else 
+ 
+ /* Beware!  This implementation resets the signal to SIG_DFL */
+ void
+ signal_no_reset(sig, func)
+ int sig;
+ RETSIGTYPE (*func) P((int));
+ {
+     int n;
+ 
+     n = signal(sig, func);
+     if (n == -1) {
+ 	perror("signal");
+         exit(1);
+     }
+ }
+ 
+ #endif
*** xntpd/ORIGntp_io.c	Mon Feb 10 17:11:19 1997
--- xntpd/ntp_io.c	Tue Feb 11 01:40:08 1997
***************
*** 2043,2067 ****
  sigio_handler(sig)
       int sig;
  {
    l_fp ts;
  
- # ifdef HAVE_SIGSET
-   /*
-    * This should not be necessary for a signal previously set with
-    * sigset().
-    */
- #  if defined(USE_SIGIO)
-   if (sigset(SIGIO, sigio_handler) == SIG_ERR)
-     msyslog(LOG_ERR, "sigio_handler: sigset(SIGIO) failed: %m");
- #  endif
- #  if defined(USE_SIGPOLL)
-   if (sigset(SIGPOLL, sigio_handler) == SIG_ERR)
-     msyslog(LOG_ERR, "sigio_handler: sigset(SIGPOLL) failed: %m");
- #  endif
- # endif /* HAVE_SIGSET */
- 
    get_systime(&ts);
    (void)input_handler(&ts);
  }
  
  /*
--- 2043,2054 ----
  sigio_handler(sig)
       int sig;
  {
+   int saved_errno = errno;
    l_fp ts;
  
    get_systime(&ts);
    (void)input_handler(&ts);
+   errno = saved_errno;
  }
  
  /*
***************
*** 2071,2121 ****
  static void
  set_signal()
  {
-   int n;
-   struct sigaction vec;
- 
-   sigemptyset(&vec.sa_mask);
- 
  #  ifdef USE_SIGIO
!   sigaddset(&vec.sa_mask, SIGIO);
! #  endif
  #  ifdef USE_SIGPOLL
!   sigaddset(&vec.sa_mask, SIGPOLL);
! #  endif
!   vec.sa_flags = 0;
! 
! #  if defined(USE_SIGIO)
!   vec.sa_handler =  sigio_handler;
! 
!   while (1)
!     {
!       n = sigaction(SIGIO, &vec, NULL);
!       if (n == -1 && errno == EINTR) continue;
!       break;
!     }
! 
!   if (n == -1)
!     {
!       perror("sigaction");
!       exit(1);
!     }
! #  endif
! #  if defined(USE_SIGPOLL)
!   vec.sa_handler =  sigio_handler;
! 
!   while (1)
!     {
!       n = sigaction(SIGPOLL, &vec, NULL);
!       if (n == -1 && errno == EINTR) continue;
!       break;
!     }
! 
!   if (n == -1)
!     {
!       perror("sigaction");
!       exit(1);
!     }
! #  endif
  }
  
  void
--- 2058,2069 ----
  static void
  set_signal()
  {
  #  ifdef USE_SIGIO
!   (void) signal_no_reset(SIGIO, sigio_handler);
! # endif
  #  ifdef USE_SIGPOLL
!   (void) signal_no_reset(SIGPOLL, sigio_handler);
! # endif
  }
  
  void
*** xntpd/ORIGntpd.c	Wed Feb  5 22:37:17 1997
--- xntpd/ntpd.c	Tue Feb 11 02:06:07 1997
***************
*** 828,838 ****
--- 828,841 ----
  moredebug(sig)
       int sig;
  {
+   int saved_errno = errno;
+ 
    if (debug < 255)
      {
        debug++;
        msyslog(LOG_DEBUG, "debug raised to %d", debug);
      }
+   errno = saved_errno;
  }
  
  /*
***************
*** 842,852 ****
--- 845,858 ----
  lessdebug(sig)
       int sig;
  {
+   int saved_errno = errno;
+ 
    if (debug > 0)
      {
        debug--;
        msyslog(LOG_DEBUG, "debug lowered to %d", debug);
      }
+   errno = saved_errno;
  }
  #else /* not DEBUG */
  /*
***************
*** 856,862 ****
--- 862,871 ----
  no_debug(sig)
       int sig;
  {
+   int saved_errno = errno;
+ 
    msyslog(LOG_DEBUG, "xntpd not compiled for debugging (signal %d)", sig);
+   errno = saved_errno;
  }
  #endif	/* not DEBUG */
  

			---  Truck