rcu: Rearrange locking in rcu_start_gp()

If CPUs are to give prior notice of needed grace periods, it will be
necessary to invoke rcu_start_gp() without dropping the root rcu_node
structure's ->lock.  This commit takes a first step in this direction
by moving the release of this lock to the end of rcu_start_gp().

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 7b1d776..2c6a931 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1521,16 +1521,14 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
                raw_spin_unlock_irqrestore(&rnp->lock, flags);
                return;
        }
-
        rsp->gp_flags = RCU_GP_FLAG_INIT;
-       raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
 
        /* Ensure that CPU is aware of completion of last grace period. */
-       rcu_process_gp_end(rsp, rdp);
-       local_irq_restore(flags);
+       __rcu_process_gp_end(rsp, rdp->mynode, rdp);
 
        /* Wake up rcu_gp_kthread() to start the grace period. */
        wake_up(&rsp->gp_wq);
+       raw_spin_unlock_irqrestore(&rnp->lock, flags);
 }
 
 /*