** Changed in: mir
Status: Fix Committed => Fix Released
--
You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to mir in Ubuntu.
https://bugs.launchpad.net/bugs/1340669
Title:
Intermittent deadlock when swithcing to session with custom display
configuration while closing other session
Status in Mir:
Fix Released
Status in Mir 0.4 series:
Won't Fix
Status in “mir” package in Ubuntu:
Fix Released
Bug description:
If when closing a session we change focus to another session that has
a custom display configuration, we may hit a deadlock.
This can been seen occasionally as a hang when logging out of an X
session under XMir. It currently only affects XMir because it is the
only production client that applies custom display configurations.
Here is how it happens:
[IPC thread]
~SessionMediator
SessionManager::close_session()
SessionManager::set_focus_to_locked(next session)
BroadcastingSessionEventSink::handle_focus_change()
MediatingDisplayChanger handles the focus change event and enqueues a display
reconfiguration action into AsioMainLoop
From this point we have two interesting execution threads:
[IPC thread continues]
~ApplicationSession
...
mir::scene::Observers::surface_removed() *** Acquires READ lock on surface
observer [1]
...
AsioMainLoop::unregister_fd_handler *** Enqueues an action into AsioMainLoop
and waits for it to complete
[MainLoop thread]
Executes display reconfiguration action:
MultiThreadedCompositor::stop()
mir::scene::Observers::remove() ** Acquires WRITE lock on observer [2]
If the IPC thread calls the surface_removed() observer before the
display reconfiguration action is executed, then the MainLoop thread
at [2] ends up waiting for a WRITE lock, but can't get it because a
READ lock has been acquired at [1]. At the same time, the IPC thread
is blocked waiting for unregister_fd_handler() to return, but it
doesn't return because the unregistration action has been enqueued
after the display reconfiguration handler which is now blocked at [2].
To manage notifications about this bug go to:
https://bugs.launchpad.net/mir/+bug/1340669/+subscriptions
--
Mailing list: https://launchpad.net/~touch-packages
Post to : touch-packages@lists.launchpad.net
Unsubscribe : https://launchpad.net/~touch-packages
More help : https://help.launchpad.net/ListHelp
