Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!itk.unit.no!ojr
From: ojr@itk.unit.no
Newsgroups: gnu.emacs.bug
Subject: emacs hangs with 100% CPU after [r]wall
Message-ID: <8904131205.AA12055@inge.itk.unit.no>
Date: 13 Apr 89 12:05:23 GMT
Sender: daemon@tut.cis.ohio-state.edu
Distribution: gnu
Organization: GNUs Not Usenet
Lines: 51


Description:
We are running SUN OS4.0.1 and emacs 18.53.3. When a broadcast message
arrives at a terminal/window where emacs is running, emacs stops
accepting input and hangs with 100% cpu being used. ^G does not work.
It is possible to restart emacs with an INT signal to the emacs
process from another window.

What I found:
Something strange happens with the SUN i/o system when a broadcast is
delivered. I looks as if no signals are delivered to the emacs process
when the signal originates in keyboard events (neither SIGINT or
SIGIO). The function 'wait_reading_process' loops forever because
select (line 1373) returns with bit 0 in 'Available' set, instead of
delivering the SIGIO signal. As this bit is ignored in the function
the result is an eternal active wait.

Solution (hack?):
What I did was checking on bit 0 in 'wait_reading_process' and sending
the missing SIGIO to emacs if the bit is set. This looks as if it
fixes the problem. The diff is listed below:

lisa% diff -c2 process.c~ process.c
*** process.c~  Sat Oct  8 17:24:20 1988
--- process.c   Thu Apr 13 11:53:26 1989
***************
*** 1399,1402 ****
--- 1399,1413 ----
            error("select error: %s", sys_errlist[xerrno]);
        }
+ #ifdef SUN_REGTEK
+       else if (nfds > 0 && (Available & 1))
+       {
+           /*
+            *  Input from standard input should go to
+            *  interrupthandler.
+            */
+ 
+           kill(getpid(), SIGIO);
+       }
+ #endif
  
        /* Check for keyboard input */

You have to have -DSUN_REGTEK in the compiler command when compiling.
process.c.

Best regards
  ojr@itk.unit.no	Ornulf Jan Rodseth
			SINTEF Dep. of Automatic Control, N-7034 TRONDHEIM
			NORWAY