Events: fixed expiration of timers in the past. If, at the start of an event loop iteration, there are any timers in the past (including timers expiring now), the ngx_process_events() function is called with zero timeout, and returns immediately even if there are no events. But the following code only calls ngx_event_expire_timers() if time actually changed, so this results in nginx spinning in the event loop till current time changes. While such timers are not expected to appear under normal conditions, as all such timers should be removed on previous event loop iterations, they still can appear due to bugs, zero timeouts set in the configuration (if this is not explicitly handled by the code), or due to external time changes on systems without clock_gettime(CLOCK_MONOTONIC). Fix is to call ngx_event_expire_timers() unconditionally. Calling it on each event loop iteration is not expected to be significant from performance point of view, especially compared to a syscall in ngx_process_events().