FreeBSD's kern_pselect installs the mask and kern_select sleeps with
PCATCH, so a pending signal that the new mask unblocks makes the call
return EINTR once the descriptors have been scanned. Here the handler ran
inside the mask swap and select then waited the full timeout, or forever
with no timeout. The swap now reports whether a handler ran, and pselect
then scans the descriptors once without waiting: a ready descriptor, a
zero timeout or an invalid argument keep select's answer, and otherwise
the call fails with EINTR and leaves the descriptor sets unchanged.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
harisibrar1