[tip/core/rcu,08/11] rcu: Clear ->rcu_read_unlock_special only once
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Message ID 20191210042629.3808-8-paulmck@kernel.org
State Accepted
Commit 3717e1e9f25ec7059e421ab6fc602cab7063c11c
Headers show
Series
  • Preemptible-RCU updates for v5.6
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Commit Message

Paul E. McKenney Dec. 10, 2019, 4:26 a.m. UTC
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(-)

Patch
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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