For example a race in managing tcb->sigprocmask may cause signal not being delivered at all.
The mechanism is as follows:
1. cpu 1: nxsig_deliver adds the signal to the sigprocmask for the duration of signal delivery
2. cpu 2: new signal (same signo) is dispatched in nxsig_tcbdispatch
3. cpu 2: nxsig_tcbdispatch detects that signal is masked
4. cpu 2: nxsig_tcbdispatch leaves critical section before calling nxsig_add_pendigsignal
5. cpu 1: nxsig_deliver finishes. The "nxsig_unmask_pendingsignal" is called in the end but does nothing
6. cpu 2: nxsig_tcbdispatch continues and adds the pending signal
In the end, the logic in the end of nxsig_deliver, which tries to handle signals added
to the pending queue during the signal action delivery (step 5) failed, and the pending signal
was not delivered.
Fix this by just keeping the critical section for during the whole duration of nxsig_tcbdispatch,
and move things which can't be executed from within critical section outside.
Signed-off-by: Jukka Laitinen <jukka.laitinen@tii.ae>
2b513af2c3