Pull RCU fix from Paul McKenney:
"A single commit that fixes a bug that was introduced a couple of merge
windows ago, but which rather more recently converged to an
agreed-upon fix. The bug is that interrupts can be incorrectly enabled
while holding an irq-disabled spinlock. This can of course result in
self-deadlocks.
The bug is a bit difficult to trigger. It requires that a preempted
task be blocking a preemptible-RCU grace period long enough to trigger
an RCU CPU stall warning. In addition, an interrupt must occur at just
the right time, and that interrupt's handler must acquire that same
irq-disabled spinlock. Still, a deadlock is a deadlock.
Furthermore, we do now have a fix, and that fix survives kernel test
robot, -next, and rcutorture testing. It has also been verified by
Sebastian as fixing the bug. Therefore..."
* 'urgent-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
rcu: Don't invoke try_invoke_on_locked_down_task() with irqs disabled
9dacf44c38