diff -r 43e37759235e -r 51a74ef9ed63 Symbian3/SDK/Source/GUID-9D00655C-AFBA-5DF7-B11B-6B2355BDF08D.dita --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Symbian3/SDK/Source/GUID-9D00655C-AFBA-5DF7-B11B-6B2355BDF08D.dita Wed Mar 31 11:11:55 2010 +0100 @@ -0,0 +1,32 @@ + + + + + +Using +SemaphoresThis document describes how to use semaphores. +

Semaphores are provided to synchronise co-operating threads. They are Kernel +objects and, as such, are managed by the Kernel.

+

Access to a semaphore is through an RSemaphore handle.

+

The semaphores are counting semaphores, having a TInt count +value that is incremented by calling the Signal() member +function of the semaphore handle and decremented by calling the Wait() member +function of the semaphore handle. A semaphore with a negative value implies +that a thread must wait for the completion of some event.

+

The mechanism by which a thread waits on a semaphore is part of the overall +management of thread scheduling.

+

For general applications, it is not common to explicitly create a semaphore; +most applications are interested in making asynchronous requests to service +providers. When a thread is created, a request semaphore is +also created that support asynchronous requests.

+

After making one or more asynchronous requests, a thread calls User::WaitForAnyRequest() +to wait for one of the requests to complete or calls User::WaitForRequest() +to wait for a specific request to complete. A service provider calls User::RequestComplete() +to signal request completion.

+
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