## Virtual Device Driver Reference for OS/2

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### Semaphore Services

VDHCreateSem Create event or mutex semaphore
VDHDestroySem Destroy semaphore
VDHPostEventSem Post event semaphore
VDHQuerySem Query semaphore state
VDHReleaseMutexSem Release mutex semaphore
VDHRequestMutexSem Request mutex semaphore
VDHResetEventSem Reset event semaphore
VDHWaitEventSem Wait on event semaphore

Note: The services above are used for synchronizing with an OS/2 process. Virtual device drivers must be careful not to block (VDHRequestMutexSem/ VDHWaitEventSem) in the context of a DOS session task. Otherwise, that task will receive no more simulated hardware interrupts until it becomes unblocked.