fork: Move thread_stack_free_rcu to call_rcu_lazy

This is required to prevent callbacks triggering RCU machinery too
quickly and too often, which adds more power to the system.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
1 file changed