k_work_* APIs cannot be used from user threads, hence it has to be
replaced with some other solution to retain userspace functionality in
the sample.
This commit reworks the sample as follows:
* Replace delayed work items with combination of k_timer and a
dedicated thread to send UDP packets. k_poll_signal is used for
communication between k_timer callback and UDP thread.
* As kernel objects should not be placed in a memory modifiable from
user threads, declare a separate structure for them, and link it
with the client context structure with a pointer.
* k_timer_init() is not a system call, therefore it has to be called
from supervisor thread. Therefore, add an additional function to
initialize UDP, and use it to initialize kernel objects used by the
UDP module and grant access for the main thread before it becomes an
user thread. UDP thread inherits permissions from the parent (main
thread).
Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>
45d9960bc6