This was added with 5ce3c9b15a ("watcher: Rebuild fdset when select()
fails"), i.e. before switching to poll(), solely to suppress errors when
FDs are closed and select() would return with an error. With poll()
this should not happen result in an error (it potentially indicates this
via POLLNVAL in revents of that FD in the array).
Because the flag was not consistently changed/read with the mutex held,
some analysis tools got confused and imagined wild deadlock scenarios.
Tobias Brunner
f5aeba0f02