Mutex Semaphore?

Hari,

Here's how you can create a counting semaphore or binary semaphore in SYS/BIOS:

Semaphore_Handle sem;

Semaphore_Params params;

Semaphore_Params_init(&params);

params.mode = Semaphore_Mode_COUNTING_PRIORITY; // or Semaphore_Mode_BINARY_PRIORITY (only with SYS/BIOS 6.34.00.10 or newer)

params.mode = Semaphore_Mode_COUNTING; // or Semaphore_Mode_BINARY for FIFO based sem

sem = Semaphore_create(count, &params, eb); // count =  1 for creating a binary semaphore. Any other count value will create a counting semaphore.

Unfortunately the release that you are using only supports FIFO based semaphores. On newer versions of BIOS (6.34.00.10 or newer) it is possible to create a PRIORITY based semaphore in addition to the FIFO based semaphore.  You could move to a newer release to get this support.

There are some additional parameters that you can specify. I have not used them in the above example. Please refer the SYS/BIOS User Guide as well the API reference for more info.

Best,

Ashish

Ashish

  Thanks. I shall update to latest SYSBIOS. 

Can you suggest how to implement a Mutex Semaphore (semMCreate()?)

I am not sure if SYSBIOS differentiates between binary semaphore and Mutex semaphore. 

Regards,

Hari

Hi Hari,

SYS/BIOS does not provide an equivalent API for semMCreate(). If you would like to create a Mutex Semaphore, you could create a wrapper for the Binary Semaphore. You would basically need a wrapper for Semaphore_create(), Semaphore_pend() and Semaphore_post().

- Semaphore_create() wrapper: Creates a semaphore and a object (structure instance) that stores the Task handle.

- Semaphore_pend() wrapper: Stores the calling Task's handle in the object and then calls Semaphore_pend().

- Semaphore_post() wrapper: Checks if the calling Task's handle matches the stored Task handle. If it matches then call Semaphore_post().

Best,

Ashish

Thanks Ashish,

   I got a following question on pthread function equivalents like pthread_mutex calls. A few of them. appreciate if you can offer a right direction in generating these APIs with SYSBIOS. 

Regards,

Hari

pthread_mutex_unlock,   //Mutex lock

pthread_mutex_lock   // Mutex_unlock

pthread_key_create

pthread_setspecific

pthread_getspecific