linux-kernel - [PATCH V2 3/7] rcu: remove useless special.b.deferred

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Message-Id: <20191102124559.1135-4-laijs@linux.alibaba.com>
Date:   Sat,  2 Nov 2019 12:45:55 +0000
From:   Lai Jiangshan <laijs@...ux.alibaba.com>
To:     linux-kernel@...r.kernel.org
Cc:     Lai Jiangshan <laijs@...ux.alibaba.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org
Subject: [PATCH V2 3/7] rcu: remove useless special.b.deferred_qs

->read_read_unlock_special.b.deferred_qs is set when
->read_read_unlock_special is non-zero, and it is cleared when
->read_read_unlock_special is cleared.

So it is useless.

Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
---
 include/linux/sched.h    | 2 +-
 kernel/rcu/tree_plugin.h | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2c2e56bd8913..3ba392d71de9 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -604,7 +604,7 @@ union rcu_special {
 		u8			blocked;
 		u8			need_qs;
 		u8			exp_hint; /* Hint for performance. */
-		u8			deferred_qs;
+		u8			pad; /* No garbage from compiler! */
 	} b; /* Bits. */
 	u32 s; /* Set of bits. */
 };
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 2fab8be2061f..f2fd7d687bdb 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -622,7 +622,6 @@ static void rcu_read_unlock_special(struct task_struct *t)
 				irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu);
 			}
 		}
-		t->rcu_read_unlock_special.b.deferred_qs = true;
 		local_irq_restore(flags);
 		return;
 	}
-- 
2.20.1