Semaphore does not use max_count

[claudiomalnati]

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Describe the set-up

any

Describe the bug (skip if none)

The CMSIS RTOS API for semaphores requires the parameter max_count for maximum number of available tokens. The current implementation however ignores this parameter making it impossible to use binary semaphores per example.

In osSemaphoreRelease(), the tx_semaphore_put() is used to release the semaphore tokens. however, this function does not account for max_count. If osSemaphoreRelease() is called more often than max_count specifies, the internal token count will exceed max_count, leading to more tokens being available, when acquireing the semaphore.

How to reproduce the bug (skip if none)

1. Create a semaphore with osSemaphoreId_t semaphore = osSemaphoreNew(1, 1, NULL);
2. Release the semaphore twice with osSemaphoreRelease(semaphore);
3. Acquire the semaphore twice in a row with osSemaphoreAcquire(semaphore, 100);
4. The second acquire should time out but is able to acquire the semaphore.

Additional context

our quick fix semaphore_max_count.patch

Screenshots

n/a

[ALABSTM]

ST Internal Reference: 198133

[ALABSTM]

Hi @claudiomalnati,

Thank you for this clear report. It has been forwarded to our development teams. I will keep you informed.

With regards,