linux-kernel - [PATCH] rcu: Remove duplicate RCU exp QS report from rcu_report

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Message-Id: <20220830083151.396561-1-qiang1.zhang@intel.com>
Date:   Tue, 30 Aug 2022 16:31:51 +0800
From:   Zqiang <qiang1.zhang@...el.com>
To:     paulmck@...nel.org, frederic@...nel.org, quic_neeraju@...cinc.com,
        joel@...lfernandes.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] rcu: Remove duplicate RCU exp QS report from rcu_report_dead()

For PREEMPT_RCU, the rcu_report_dead() is invoked means that the
outgoing CPU mask is clear from leaf rcu_node and has no further
need of RCU, so invoke rcu_preempt_depth() return value is always
zero in rcu_report_dead(), if the current outgoing CPU rcu_data
structure's cpu_no_qs.b.exp is true, the rcu_preempt_deferred_qs()
will invoke rcu_report_exp_rdp() to report exp QS.

for non-PREEMPT_RCU, the rcu_preempt_deferred_qs() is equivalent to
rcu_report_exp_rdp().

Signed-off-by: Zqiang <qiang1.zhang@...el.com>
---
 kernel/rcu/tree.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 6bb8e72bc815..0ca21ac0f064 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4276,8 +4276,6 @@ void rcu_report_dead(unsigned int cpu)
 	// Do any dangling deferred wakeups.
 	do_nocb_deferred_wakeup(rdp);

-	/* QS for any half-done expedited grace period. */
-	rcu_report_exp_rdp(rdp);
 	rcu_preempt_deferred_qs(current);

 	/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
-- 
2.25.1