tree e644552b4dbd9f601765695372566c03975a4739
parent afe1de664ef3cb756e70938d99417dcbc6b1379a
author Doug Ledford <dledford@redhat.com> 1418230019 -0500
committer Roland Dreier <roland@purestorage.com> 1418695874 -0800

IPoIB: Make the carrier_on_task race aware

We blindly assume that we can just take the rtnl lock and that will
prevent races with downing this interface.  Unfortunately, that's not
the case.  In ipoib_mcast_stop_thread() we will call flush_workqueue()
in an attempt to clear out all remaining instances of ipoib_join_task.
But, since this task is put on the same workqueue as the join task,
the flush_workqueue waits on this thread too.  But this thread is
deadlocked on the rtnl lock.  The better thing here is to use trylock
and loop on that until we either get the lock or we see that
FLAG_ADMIN_UP has been cleared, in which case we don't need to do
anything anyway and we just return.

Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>