Cache: proper wakeup of subrequests. In case of a cache lock timeout and in the aio handler we now call r->write_event_handler() instead of a connection write handler, to make sure to run appropriate subrequest. Previous code failed to run inactive subrequests and hence resulted in suboptimal behaviour, see report by Yichun Zhang: http://mailman.nginx.org/pipermail/nginx-devel/2013-October/004435.html (Infinite hang claimed in the report seems impossible without 3rd party modules, as subrequests will be eventually woken up by the postpone filter.)