tree 0aaa08c78c1d7ae0f3050637e7df4b369f11b48c
parent 115a025db36b625510fb41a65e1f4fa3cf38b9db
author Frederic Weisbecker <fweisbec@gmail.com> 1339243590 +0200
committer Paul E. McKenney <paulmck@linux.vnet.ibm.com> 1339443187 -0700

rcu: Allow calls to rcu_exit_user_irq from nesting irqs

rcu_exit_user_irq() which exits RCU idle mode after the current
irq returns has been designed to be called from non nesting irqs
only.

However the IPI that restarts the tick and exits RCU user-idle mode
in nohz cpusets can happen anytime. For example it can be a nesting
irq by interrupting a softirq. In this case the stack of RCU API
calls becomes:

==> IRQ
    rcu_irq_enter()
    ....
    do_softirq {
===== > IRQ (restart tick IPI)
        rcu_irq_enter()
        rcu_exit_user_irq()
        rcu_irq_exit()
<=====
    }
    rcu_irq_exit();

Hence we need to make rcu_exit_user_irq() callable from any nesting
level of interrupt.

v2: rcu_user_enter_irq() is only called from non nesting irqs though so
the change doesn't need to be propagated to it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>