Avoid issues with interrupts and priority inversions and other deadlocks
and use a SW based random generator for LWIP when under FreeRTOS.
This means removing any overrides for sleep_until and the two
get_rand_xx calls from the SDK, making things much saner.
Related to #1883, #1872, and other random FreeRTOS lockups.
Fixes#1394
The Pico_Rand SDK calls gather bits from the HW ROSC at precise intervals.
If there is jitter in the sleep_until() call then the ROSC bit collection
will always think it's failed to acquire the right bit and retry infintitely.
Avoid by wrapping the HW random number calls and the sleep_until() routine.
Only when in FreeRTOS set a flag to silently make sleep_until() into a
busy wait loop while in a random number generation step. When not in the
random code, do the normal sleep_until call.
The stdin/stdout FILEs have an internal mutex which needs to be initted
to a FreeRTOS one, or any sketch with ::printf will hang. Automatically
create and acquire/release the shadowed mutex.
Requires new build of pico-quick-toolchain to function properly. Tested
on preliminary local build.
There's a memory leak around the corner: creating the mutex means
that we allocate memory for it, but if we cannot find any free slot in the
FMMap array, we're simply returning a nullptr without ever freeing the
previously allocated memory.
Instead of allocating it out of the free-slot check, do it inside.
While at it, also check if the mutex creation succeeded before assigning
it to a FMMap slot.
Fixes#795
Replace all CoreMutex and Newlib mutex accesses with FreeRTOS calls
when in FreeRTOS mode. Avoid issues with hange/etc. due to priority
inversion.
No changes to normal operating mode.
Add a FreeRTOS stress test that caught the issue fixed here.
