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commented
9 years ago Found the problem. ARC bites again :(
In TIdListenerThread.Run() before a client is accepted, TIdTCPServer retrieves
a new Yarn from its Scheduler. Using the default Scheduler, a new thread is
created at that time, but in a suspended state. The thread is resumed when a
client connects and a TIdContext task is assigned to the thread. But when there
is no client connected yet, the thread remains suspended.
During server shutdown, TIdTCPServer asks the Scheduler to terminate its active
Yarns. However, TIdSchedulerOfThread.TerminateYarn() was using FreeAndNil() to
free a Yarn that does not have a running thread, and that does not work under
ARC because the Yarn is referenced by its thread and vice versa, so the Yarn's
refcount was not falling to 0 and thus the Yarn was not being freed (and more
importantly, its thread was not being resumed and terminated correctly). So the
Yarn was not getting removed from the Scheduler's list of active Yarns, and
TIdTCPServer ended up stuck in a loop waiting for active Yarns to clear out but
they never did. Hense the shutdown deadlock.
This does not happen on desktop systems, where FreeAndNil() frees the Yarn
immediately, so everything gets cleared out as expected.
Fixed in rev 5140 by replacing FreeAndNil() with IdDisposeAndNil() in
TIdSchedulerOfThread.TerminateYarn().
Original comment by gambit47 on 30 May 2014 at 2:34
- Changed state: Fixed
Original issue reported on code.google.com by
gambit47on 28 May 2014 at 8:22