RTOS: Semaphore for 1 resource but will be post many times

jimmy

Tool/software: TI-RTOS

Hi,

It is said on page 110 of Bios_User_Guide(which comes with the latest BLE 3.0 stack SDK simplelink_cc2640r2_sdk_1_30_00_25) that :

"The maximum count value for a semaphores plus one is the number of tasks a counting semaphore can coordinate"

In my project , there are three work task :The first one is a consumer and the others are both producers.

The consumer will pend on the semaphore so this task waits for signals from producers.
I have a question now. As is stated in the guide , the max counting value of this semaphore will be 2 (2 + 1 =3), right?

So when the consumer is doing something (may be time-consuming) and the two producers post more than 2 signals during this period, some events will lost (since the counting value of this semaphone cound not exceed 2).

How can I deal with this situation?

over 9 years ago

0 ToddMullanix over 9 years ago

TI__Guru* 96960 points

Hi,

Not sure how that comment got into the UG...it's wrong! I've opened a doc bug for this.

There should be mention that the counter is 16 bits and that with Asserts disabled, a rollover condition will result in the Semaphore quietly becoming empty on a subsequent Semaphore_pend() call.

Todd

0 jimmy over 9 years ago in reply to ToddMullanix

Intellectual 400 points

So, it is OK for me to count the value of the signals with a signle semaphore ?

0 ToddMullanix over 9 years ago in reply to jimmy

TI__Guru* 96960 points

I don't understand your question.

0 jimmy over 9 years ago in reply to ToddMullanix

Intellectual 400 points

In my mind, the current count value of a semaphores means the available resource we can use now.

For example, if the producer task call semaphore_post 5 times, the count value of the semaphore should be 5, right?

I am worrying about the limitation of the max count value of semaphore it TI RTOS, which is stated that "The maximum count value for a semaphores plus one is the number of tasks a counting semaphore can coordinate".

So, I just want to make sure that in a project (1 consumer and 2 producers) if producer tasks have called semaphore_post 5 times, what is the real value of the semaphore? 5 or 2? (2 is the value I got from the document, since the number of tasks the semaphore can coordinate is 3, 3 - 1 = 2).

0 Michel Solecki over 9 years ago in reply to jimmy

Mastermind 8415 points

Hi,
As Todd has mentioned in his previous, the semaphore count would be 5.
And as he mentioned as well, if you were to post a semaphore when the count is 65535, the count would return to 0 (i.e. empty).
Regards,
Michel

0 jimmy over 9 years ago in reply to Michel Solecki

Intellectual 400 points

Thank you very much!

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RTOS: Semaphore for 1 resource but will be post many times