Revision 1891716

mpm_event: Fix queues' maintenance and linger timeouts on graceful restart/stop

* server/mpm/event/event.c (abort_socket_nonblocking): Renamed to
  close_socket_nonblocking_() with close_socket_nonblocking() as a macro to
  APLOG_TRACE8 the caller __FUNCTION__ and __LINE__. Do nothing if the socket
  is closed already, e.g. from close_worker_sockets().

* server/mpm/event/event.c (close_worker_sockets): Let defer_linger_chain be
  cleaned by the terminating workers.

* server/mpm/event/event.c (wakeup_listener): Add a trace8 of the call.

* server/mpm/event/event.c (decrement_connection_count): Add a trace8 of the
  call, decrement lingering_count from CONN_STATE_LINGER too which may happen
  from start_lingering_close_blocking() on ap_start_lingering_close() failure,
  and when dying call ap_queue_interrupt_one() from there instead of
  close_connection() so that we don't miss a worker_thread_should_exit_early()
  case.

* server/mpm/event/event.c (start_lingering_close_blocking): Don't increment
  lingering_count when it's already done by defer_lingering_close() (i.e.
  cs->deferred_linger is set), set socket timeout to 2s (SECONDS_TO_LINGER)
  before pre_close hooks and then after let socket timeout handling to
  process_lingering_close().

* server/mpm/event/event.c (start_lingering_close_nonblocking): Rename to
  defer_lingering_close(), add trace6 of the call, set CONN_STATE_LINGER so
  that the connection is accounted for until handled by a worker, and let
  start_lingering_close_blocking() know by setting cs->deferred_linger.

* server/mpm/event/event.c (stop_lingering_close): Rename to close_connection()
  and log the call at trace6 level instead of trace4 (for consistency), and use
  it everywhere apr_socket_close()+ap_queue_info_push_pool() is open coded.

* server/mpm/event/event.c (shutdown_connection): This helper can be called
  anywhere where nonblocking is required to either initiate short lingering
  close or directly close if the connection is lingering already. It's used 
  as a generic process_timeout_queue() callback to terminate expired entries
  in any state.

* server/mpm/event/event.c (update_reqevents_from_sense): Allow to specify the
  sense as argument where -1 means cs->pub.state as before, and call it from
  everywhere before adding to the pollset such that APR_POLL* events are set
  fully/appropritely regardless of the underlying pollset implementation.

* server/mpm/event/event.c (process_socket): Gracefuly stop the process on
  pollset errors, and don't forcibly close the connection if listener_may_exit
  when ap_run_input_pending() determines that the next request is already here.

* server/mpm/event/event.c (close_listeners): Add trace6 of the call, and
  return whether it's the first close or not.

* server/mpm/event/event.c (push2worker): Call shutdown_connection() on failure
  when cs is available so that pre_close hooks (h2 flush, ssl close notify) are
  still called.

* server/mpm/event/event.c (process_lingering_close): Add trace6 of the call,
  always set timeout to zero (hence nonblocking) before reading pending data,
  and terminate the process gracefuly on pollset errors.

* server/mpm/event/event.c (listener_thread): Add some trace7 messages around
  poll()ing for debug, round poll()ing timeout to the upper millisecond to work
  around the rounding down done by some pollset implementations, and on the
  first call to close_listeners() when listener_may_exit->dying let's force the
  maintenance of the queues to kill keep alive connections and apply shorter
  lingering close timeout to free worker threads faster for the next generation.

* server/mpm/event/event.c (join_workers): Rewrite the !dying loop to avoid
  "listener has not stopped accepting yet" if sleeping 500ms once did it.

Github: #208