@CHIP-RTOS C Library - RTOS API

Reserve a resource semaphore. If current task is already the owner of this semaphore then the semaphore's usage count is incremented by one and the function returns immediately with success.

int RTX_Reserve_Sem ( int semID, long far *time_ms );

Parameters

semID: The semaphore ID of a resource semaphore acquired by a call to RTX_Create_Sem.
time_ms: Pointer for ms to wait: Zero -> Wait forever for semaphore
Positive value -> Maximum number of milliseconds to wait for resource
Negative value -> Polling mode, return immediately. If semaphore was not available the return value will be the -27 time-out indication.

Return Value

0 on success else error code.

Comments

The calling task will be suspended waiting for the resource if the resource is owned by some other task.

When the resource is finally available for use by the caller, the procedure will return with 0.

Upon first acquiring ownership of the resource, the resouce's usage count is set to one.

It is permissible for a task to call RTX_Reserve_Sem even if the calling task already owns the resource. The resource usage count is incremented by one for each subsequent call by the resource owner.

The wait priority used here is 20. (See the RTX_Wait_Sem_Priority alternative API for explanation of wait priority.)

RTOS API

This library function invokes a RTOS software interrupt. Refer to this RTOS API function's documentation for more details.

Supported since or modified in @CHIP-RTOS version

SC12 SC13 SC11 SC1x3 SC2x V1.00 V1.00 V1.00 V0.90 V1.00

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