tree 7c225c914aabb54c7ce3add5917386f27e67990a
parent b6331ae8afe4118884c4b6e14a213758d88422b2
author Oleg Nesterov <oleg@redhat.com> 1411940661 +0200
committer Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1415903740 -0800

rcu: More info about potential deadlocks with rcu_read_unlock()

The comment above rcu_read_unlock() explains the potential deadlock
if the caller holds one of the locks taken by rt_mutex_unlock() paths,
but it is not clear from this documentation that any lock which can
be taken from interrupt can lead to deadlock as well and we need to
take rt_mutex_lock() into account too.

The problem is that rt_mutex_lock() takes wait_lock without disabling
irqs, and thus an interrupt taking some LOCK can obviously race with
rcu_read_unlock_special() called with the same LOCK held.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>