QUEUED SIGNAL ACTIONS ARE INAPPROPRIATELY DEFERRED

```
Description: The implement of nxsig_deliver() does the following in a loop:
- It takes the next next queued signal action from a list
- Calls the architecture-specific up_sigdeliver() to perform
the signal action (through some sleight of hand in
up_schedule_sigaction())
- up_sigdeliver() is a trampoline function that performs the
actual signal action as well as some housekeeping functions
then
- up_sigdeliver() performs a context switch back to the normal,
uninterrupted thread instead of returning to nxsig_deliver().

The loop in nxsig_deliver() then will have the opportunity to
run until when that normal, uninterrupted thread is suspended.
Then the loop will continue with the next queued signal
action.

Normally signals execute immediately. The is the whole reason
why almost all blocking APIs return when a signal is received
(with errno equal to EINTR).
Status: Open
Priority: Low. This design flaw has been around for ages and no one has yet
complained about it. Apparently the visibility of the problem is
very low.
```