It seems that current _cygtls::handle_SIGCONT() code sometimes falls
into a deadlock due to frequent TLS lock/unlock operation in the
yield() loop. With this patch, the yield() in the wait loop is placed
outside the TLS lock to avoid frequent TLS lock/unlock.
Fixes: 9ae51bcc51a7 ("Cygwin: signal: Fix another deadlock between main and sig thread")
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>