Gain access to a semaphore in shared mode
Source position: exec.pas line 1324
procedure ObtainSemaphoreShared( |
SigSem: PSignalSemaphore |
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SigSem |
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An initialized signal semaphore structure |
A lock on a signal semaphore may either be exclusive, or shared. Exclusive locks are granted by the ObtainSemaphore() and AttemptSemaphore() functions. Shared locks are granted by ObtainSemaphoreShared(). Calls may be nested.
Any number of tasks may simultaneously hold a shared lock on a semaphore. Only one task may hold an exclusive lock. A typical application is a list that is often read, but only occasionally written to.
Any exlusive locker will be held off until all shared lockers release the semaphore. Likewise, if an exlusive lock is held, all potential shared lockers will block until the exclusive lock is released. All shared lockers are restarted at the same time.
A task owning a shared lock must not attempt to get an exclusive lock on the same semaphore.
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Get a List of semaphores |
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Initialize a signal semaphore |
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Make signal semaphore available to others |
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Try to obtain a Semaphore without blocking |
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Gain exclusive access to a semaphore |
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Asynchron locking of a semaphore |
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Release a bidMessage from Procure() |