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Corrections
 
A registered mouse subsystem should not issue MouSynch when the base video
subsystem (BVS) issues MouOpen and MouClose functions. A registered mouse
subsystem must provide the required level of serialization for MouOpen and
MouClose without calling MouSynch. This special processing is required
because MouOpen and MouClose are issued by BVS on the VioSetMode path. The
VioSetMode function can be issued, in turn, by a VioSavRedrawWait thread.
You can assume the synchronization semaphore was already held by another
thread blocked by a call to MouReadEventQue.
 
Note that if a save/redraw wait thread issues the VioSetMode function, if
BVS in turn issues the MouOpen or MouClose function, and the mouse subsystem
in turn issues the MouSynch function, the screen switch will be blocked and
the system will "hang."
 
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