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From:   Zqiang <qiang.zhang1211@gmail.com>
To:     paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com,
        joel@joelfernandes.org, qiang.zhang1211@gmail.com
Cc:     rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] srcu: Priority check rcu_gp_is_expedited() in synchronize_srcu()
Date:   Tue,  4 Jul 2023 15:08:09 +0800
Message-Id: <20230704070809.31951-1-qiang.zhang1211@gmail.com>
Precedence: bulk

Since the atomic variable rcu_expedited_nesting is initialized to
true, so the rcu_gp_is_expedited() is always return true during
system startup until the rcu_end_inkernel_boot() is called. this
means that without setting rcupdate.rcu_normal=1 and before the
rcu_end_inkernel_boot() is executed, regardless of whether the
return value of srcu_might_be_idle() is true, call synchronize_srcu()
always fall back to synchronize_srcu_expedited(), so there is
no need to checking srcu_might_be_idle() return value.

For the rcupdate.rcu_normal=0, rcupdate.rcu_normal_after_boot=0 and
rcupdate.rcu_expedited=1 kernels, there is also no need to checking
srcu_might_be_idle() return value.

This commit therefore priority check rcu_gp_is_expedited() return value
in synchronize_srcu().

Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
---
 kernel/rcu/srcutree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 20d7a238d675..a819f11d9b90 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1435,7 +1435,7 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
  */
 void synchronize_srcu(struct srcu_struct *ssp)
 {
-	if (srcu_might_be_idle(ssp) || rcu_gp_is_expedited())
+	if (rcu_gp_is_expedited() || srcu_might_be_idle(ssp))
 		synchronize_srcu_expedited(ssp);
 	else
 		__synchronize_srcu(ssp, true);
-- 
2.17.1