Update of /usr/local/src/cvs/bordeaux-mp In directory loaclhost.telent.net:/tmp/cvs-serv1400
Modified Files: Specification Log Message: more bug fixes, courtesy Robert Strandh
Index: Specification =================================================================== RCS file: /usr/local/src/cvs/bordeaux-mp/Specification,v retrieving revision 1.7 retrieving revision 1.8 diff -u -d -r1.7 -r1.8 --- Specification 12 Jul 2004 23:41:50 -0000 1.7 +++ Specification 15 Jul 2004 15:26:51 -0000 1.8 @@ -211,20 +211,22 @@ 2) A processes and removes all events that are available in C 3) When C is empty, A calls CONDITION-WAIT, which atomically releases the lock and puts A to sleep on CV -4) Loop back to step 1, for as long as processing should continue +4) Wait to be notified; CONDITION-WAIT will acquire the lock again + before returning +5) Loop back to step 2, for as long as processing should continue
When B generates an event E, it 1) acquires the lock guarding C 2) adds E to the channel -3) releases the lock -4) calls CONDITION-NOTIFY on CV to wake any sleeping process +3) calls CONDITION-NOTIFY on CV to wake any sleeping process +4) releases the lock
To avoid the "lost wakeup" problem, the implementation must guarantee -that CONDITION-WAIT in process A atomically release the lock and +that CONDITION-WAIT in process A atomically releases the lock and sleeps. If this is not guaranteed there is the possibility that process B can add an event and call CONDITION-NOTIFY between the lock release and the sleep - in this case the notify call would not see A, -which would be left sleeping despite there being events available. +which would be left sleeping despite there being an event available.
make-condition-variable () [function]