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Aucbvax.3178 fa.unix-wizards utzoo!decvax!ucbvax!unix-wizards Wed Sep 16 13:33:34 1981 signals and events >From cbosg!ewl@Berkeley Wed Sep 16 13:27:53 1981 I am looking at the possibility of adding Events to UNIX and changing parts of the Signal mechanism. Events could be defined for use between user processes (perhaps they would be similar to VMS events) or between a user and the system kernel, to indicate things like "you just received 20 characters on line 7" or "a child just died" or "your write completed, you may reuse the buffer", etc. It is not clear whether this can be done in a way that is upward compatible with current systems, nor what events should be allowed and how events could be defined dynamically. If events existed, which should be available and how should they be implemented? Should they be asynchronous, like Signals, or should they be deliberately waited for and perhaps have a general "an event occurred" signal?

Signals could (should?) be changed to allow them to be temporarily ignored and queued while masked and made so that none slip through the cracks due to races when reenabling. Perhaps something similar to UCB 4.1BSD sigsys(2) (or to one of the others that have been proposed) should be implemented as a (BTL) standard?

Many people have mumbled something about wanting a different kind of signals or having user/kernel events or messages. My task is to see if people realy want it and if it would be worth it to make rather fundamental changes to the nature of (BTL) UNIX.

For BTL folks, I have an even more long-winded MF version of this news item. However, I am interested in the opinions of all UNIX followers, both BTL and outsiders. I may be reached at: Bill Leggett cbosg!ewl csvax.ewl@berkeley Bell Laboratories 6200 E Broad St., Columbus OH 43213 (614)-868-4464 There is, of course, no guarantee that any changes will be made nor that any options I might develop would become available in standard UNIX from BTL. The current thinking is that signals should not be changed and events not added. However, my long-term goal is to produce aids for those designing real-time cooperating process systems, so any thoughts about signals, events, language features, IPC mechanisms, etc., will be appreciated, even though non-BTLers may see no changes to standard (BTL) UNIX for quite a while.

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