Inserting a semaphore into ch_thread

[szekelyisz]

Hi,

full-duplex socket operation in LWIP 2.0 requires a dedicated semaphore per thread. I found the CH_CFG_THREAD_EXTRA_FIELDS macro which enables additional fields in the thread structure with CH_CFG_THREAD_INIT_HOOK and CH_CFG_THREAD_EXIT_HOOK to initialize and finalize them. So far so good.

But if I add a struct ch_semaphore as a new field, I get "has incomplete type" compilation errors from all around the OS code, which is understandable.

If I add a struct ch_semaphore*, I need to actually allocate the memory for the semaphore, which can be done with CH_CFG_THREAD_INIT_HOOK but I have no idea how to allocate memory there as chHeapAlloc() cannot be called from a lock zone in which _thread_init (that calls CH_CFG_THREAD_INIT_HOOK) resides. Allocating the memory with chCoreAllocI() seems like a bad idea as it can't be freed.

Any idea what the solution is here? Thanks!

[Giovanni]

Hi,

You could use a memory pool feeding from the core allocator, the memory would be returned to the pool.

Giovanni

[szekelyisz]

Thanks Giovanni, but I found my way around this. LWIP provides the LWIP_NETCONN_THREAD_SEM_ALLOC() and LWIP_NETCONN_THREAD_SEM_FREE() macros which are called if the thread semaphore is invalid (as defined by the sys_sem_valid() function in sys_arch.c) or not needed anymore, respectively. This enables any type of allocation.