[PATCH tip/core/rcu 10/15] rcu: Rearrange locking in rcu_start_gp()

From: Paul E. McKenney
Date: Mon Mar 18 2013 - 17:37:09 EST

From: "Paul E. McKenney" <paul.mckenney@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
kernel/rcutree.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 7b1d776..2c6a931 100644
--- 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);
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. */
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);


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