For the caller there should be no difference if there is no message
in the queue and if there can't be a message in the queue.
The current API works as one would expect if there is a message queue,
but once called from a thread that does not have a message queue
configured, code that does
while (msg_avail())
will end up in an infinite loop.
Remove this foot-gun from the API by making the return value of
msg_avail() independend of the availability of a message queue.
Currently it is not possible to check if a message was sent over a bus
or if it was send the usual way using `msg_send()`.
This adds a flag to the `sender_pid` if the message was sent over a bus.
`MAXTHREADS` is currently set to 32, so there is still plenty of room in
the PID space. (`kernel_pid_t` is `int16_t`)
The message type for bus message type is already accessed through a getter
function, so it's just consistent to do the same for sender_pid.
Replace accesses to `sched_active_thread`, `sched_active_pid`, and
`sched_threads` with `thread_get_active()`, `thread_get_active_pid()`, and
`thread_get_unchecked()` where sensible.
As discussed in #2725, this commit renames a number of stacksize constants to
better convey their intended usage. In addition, constants for thread priority
are given a `THREAD_` prefix. Changes are:
* KERNEL_CONF_STACKSIZE_PRINTF renamed to THREAD_EXTRA_STACKSIZE_PRINTF
* KERNEL_CONF_STACKSIZE_DEFAULT renamed to THREAD_STACKSIZE_DEFAULT
* KERNEL_CONF_STACKSIZE_IDLE renamed to THREAD_STACKSIZE_IDLE
* KERNEL_CONF_STACKSIZE_MAIN renamed to THREAD_STACKSIZE_MAIN
* Move thread stacksizes from kernel.h to thread.h, since the prefix changed
* PRIORITY_MIN renamed to THREAD_PRIORITY_MIN
* PRIORITY_IDLE renamed to THREAD_PRIORITY_IDLE
* PRIORITY_MAIN renamed to THREAD_PRIORITY_MAIN
* Move thread priorities from kernel.h to thread.h since the prefix has changed
* MINIMUM_STACK_SIZE renamed to THREAD_STACKSIZE_MINIMUM for consistency
msg_send_int() sets `m->sender_pid = target_pid`. This was used to flag a
message as having been sent by an ISR.
This PR introduces a static inline function `msg_sent_by_int()` and a
specific define for this purpose.
`thread.c` initializes a thread with an empty message queue. `cib_put()`
will `return -1` for an empty CIB, so there is no need to test if
`thread->msg_array != NULL`.
