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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     "Paul E. McKenney" <paulmck@kernel.org>,
        "Xu, Yanfei" <yanfei.xu@windriver.com>,
        Sasha Levin <sashal@kernel.org>, rcu@vger.kernel.org
Subject: [PATCH AUTOSEL 5.13 06/19] rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader()
Date:   Thu, 22 Jul 2021 23:57:07 -0400
Message-Id: <20210723035721.531372-6-sashal@kernel.org>
In-Reply-To: <20210723035721.531372-1-sashal@kernel.org>
References: <20210723035721.531372-1-sashal@kernel.org>
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From: "Paul E. McKenney" <paulmck@kernel.org>

[ Upstream commit a9ab9cce9367a2cc02a3c7eb57a004dc0b8f380d ]

Invoking trc_del_holdout() from within trc_wait_for_one_reader() is
only a performance optimization because the RCU Tasks Trace grace-period
kthread will eventually do this within check_all_holdout_tasks_trace().
But it is not a particularly important performance optimization because
it only applies to the grace-period kthread, of which there is but one.
This commit therefore removes this invocation of trc_del_holdout() in
favor of the one in check_all_holdout_tasks_trace() in the grace-period
kthread.

Reported-by: "Xu, Yanfei" <yanfei.xu@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/rcu/tasks.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 71e9d625371a..fcef5f0c60b8 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -937,7 +937,6 @@ static void trc_wait_for_one_reader(struct task_struct *t,
 	// The current task had better be in a quiescent state.
 	if (t == current) {
 		t->trc_reader_checked = true;
-		trc_del_holdout(t);
 		WARN_ON_ONCE(t->trc_reader_nesting);
 		return;
 	}
-- 
2.30.2