in SMP, signal processing cannot be nested, we use xcp.sigdeliver to identify whether there is currently a signal being processed, but this state does not match the actual situation
One possible scenario is that signal processing has already been completed, but an interrupt occurs, resulting in xcp.sigdeliver not being correctly set to NULL,
At this point, a new signal arrives, which can only be placed in the queue and cannot be processed immediately
Our solution is that signal processing and signal complete status are set in the same critical section, which can ensure status synchronization
Signed-off-by: hujun5 <hujun5@xiaomi.com>