[PATCH 8/8] rcu: remove irq work for rsp_wakeup()

[Lai Jiangshan <laijs@cn.fujitsu.com>]

It is safe to aquire scheduler lock in rnp->lock since the rcu read lock is
always deadlock-immunity(rnp->lock is always can't be nested in scheduler lock)

it partial revert patch 016a8d5b.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
 kernel/rcutree.c |   17 ++---------------
 kernel/rcutree.h |    1 -
 2 files changed, 2 insertions(+), 16 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index e08abb9..6c91edc 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1524,14 +1524,6 @@ static int __noreturn rcu_gp_kthread(void *arg)
 	}
 }
 
-static void rsp_wakeup(struct irq_work *work)
-{
-	struct rcu_state *rsp = container_of(work, struct rcu_state, wakeup_work);
-
-	/* Wake up rcu_gp_kthread() to start the grace period. */
-	wake_up(&rsp->gp_wq);
-}
-
 /*
  * Start a new RCU grace period if warranted, re-initializing the hierarchy
  * in preparation for detecting the next grace period.  The caller must hold
@@ -1556,12 +1548,8 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
 	}
 	rsp->gp_flags = RCU_GP_FLAG_INIT;
 
-	/*
-	 * We can't do wakeups while holding the rnp->lock, as that
-	 * could cause possible deadlocks with the rq->lock. Deter
-	 * the wakeup to interrupt context.
-	 */
-	irq_work_queue(&rsp->wakeup_work);
+	/* Wake up rcu_gp_kthread() to start the grace period. */
+	wake_up(&rsp->gp_wq);
 }
 
 /*
@@ -3153,7 +3141,6 @@ static void __init rcu_init_one(struct rcu_state *rsp,
 
 	rsp->rda = rda;
 	init_waitqueue_head(&rsp->gp_wq);
-	init_irq_work(&rsp->wakeup_work, rsp_wakeup);
 	rnp = rsp->level[rcu_num_lvls - 1];
 	for_each_possible_cpu(i) {
 		while (i > rnp->grphi)
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index a5e9643..5892a43 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -449,7 +449,6 @@ struct rcu_state {
 	char *name;				/* Name of structure. */
 	char abbr;				/* Abbreviated name. */
 	struct list_head flavors;		/* List of RCU flavors. */
-	struct irq_work wakeup_work;		/* Postponed wakeups */
 };
 
 /* Values for rcu_state structure's gp_flags field. */
-- 
1.7.4.4