Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!rpi!ander
From: ander@pawl.rpi.edu (Michael R. Primm)
Newsgroups: comp.os.os2
Subject: Re: signals, threads, and memory allocation
Message-ID: <1989Nov11.170106.1088@rpi.edu>
Date: 11 Nov 89 17:01:06 GMT
References: <32295@ucbvax.BERKELEY.EDU> <8551@microsoft.UUCP> <2602@auspex.auspex.com> <8714@microsoft.UUCP> <2620@auspex.auspex.com>
Organization: Rensselaer Polytechnic Institute, Troy NY
Lines: 24

According to "Advanced OS/2 Programming" by Microsoft Press, when a signal
handler is invoked, no further signals of that type are processed until
DosSetSigHandler() is called again with an action code of 4 (reset current
signal).
   Also, DosHoldSignal() can be used to temporarily postpose signal
handling (signals generated while a hold is in effect are not lost, but
wait until the hold ends).
   As far as I can tell, "masking" signals can be done by simply setting
them to have a handler which does nothing but reset the current signal (
or possibly nothing, but I'm not sure if some additional burden would be
put on the system by accumulating signals (if they do accumulate...I tend
to doubt it, since OS/2's signals are meant to emulate hardware interrupts)).
If you wanted to, writing up a routine which could enable and disable 
signals using a mask should be easy....just keep a static array of pointers
to each signal handler, define a "null" handler routine, and have the routine
remake a DosSetSigHandler call for each signal which changes state (enabled to
disabled, or vice versa).
   Basically, OS/2's kernal support is complete enough to generate pretty much 
any service you want....since most of the calls are supported as DLLs, anyone
can write up additional services which can work just as well.  IMHO, its
kinda nice having access to lower level calls...you don't have a specific
philosophy imposed upon you as much as on other systems (i.e. you can have
any semaphores you want, as long as they're FIFO, etc).
                                                       --Mike Primm