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[Launchpad Bug Tracker <1194384@xxxxxxxxxxxxxxxxxx>]

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Mir clients may not be aware, but the callbacks made by libmirclient are
not thread safe in any way.

An apparently simple single-threaded Mir client has 3 threads, which can
execute concurrently:

1. The "main" thread, where the initial connection was made.
2. The socket thread, where the protocol is handled (mir_connected_callback, mir_surface_callback, MirSurfaceEvent)
3. The input thread, where input events are received (MirMotionEvent, MirKeyEvent)

Yes, you could receive a MirSurfaceEvent and MirMotionEvent
simultaneously in different threads. Neither of which are the main
thread.

This is how a Mir client works. Unfortunately the existence of these
threads is not yet documented. I will update the docs. But this bug is
really about finding a way to make the client API more thread safe for
simple toolkits and clients that normally don't care about threads.
UPDATE: Client API docs improved in r789.

To make matters worse, the client API functions are generally not thread
safe either: mir_surface_* mir_connection_*. So libmirclient forces you
to run in multiple threads and yet doesn't protect you at all against
races and corruption that could arise from calling libmirclient from
varying threads. UPDATE: Fixed in r827

** Affects: mir
     Importance: High
         Status: Triaged

** Affects: xorg-server (Ubuntu)
     Importance: Wishlist
         Status: Confirmed


** Tags: clientapi input qa-touch
-- 
Mir client callbacks are not thread-safe
https://bugs.launchpad.net/bugs/1194384
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