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Subject[PATCH tip/core/rcu 08/11] rcu: Clear ->rcu_read_unlock_special only once
Date
From: Lai Jiangshan <laijs@linux.alibaba.com>

In rcu_preempt_deferred_qs_irqrestore(), ->rcu_read_unlock_special is
cleared one piece at a time. Given that the "if" statements in this
function use the copy in "special", this commit removes the clearing
of the individual pieces in favor of clearing ->rcu_read_unlock_special
in one go just after it has been determined to be non-zero.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tree_plugin.h | 19 +++----------------
1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 7487c79..c3a3271 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -444,16 +444,9 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
local_irq_restore(flags);
return;
}
- t->rcu_read_unlock_special.b.exp_hint = false;
- t->rcu_read_unlock_special.b.deferred_qs = false;
- if (special.b.need_qs) {
+ t->rcu_read_unlock_special.s = 0;
+ if (special.b.need_qs)
rcu_qs();
- t->rcu_read_unlock_special.b.need_qs = false;
- if (!t->rcu_read_unlock_special.s && !rdp->exp_deferred_qs) {
- local_irq_restore(flags);
- return;
- }
- }

/*
* Respond to a request by an expedited grace period for a
@@ -461,17 +454,11 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
* tasks are handled when removing the task from the
* blocked-tasks list below.
*/
- if (rdp->exp_deferred_qs) {
+ if (rdp->exp_deferred_qs)
rcu_report_exp_rdp(rdp);
- if (!t->rcu_read_unlock_special.s) {
- local_irq_restore(flags);
- return;
- }
- }

/* Clean up if blocked during RCU read-side critical section. */
if (special.b.blocked) {
- t->rcu_read_unlock_special.b.blocked = false;

/*
* Remove this task from the list it blocked on. The task
--
2.9.5
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