linux-kernel - [PATCH v3 01/14] ACPI: APEI: Remove redundant rcu_read_lock/unlock() in spin

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Message-Id: <20250916044735.2316171-2-dolinux.peng@gmail.com>
Date: Tue, 16 Sep 2025 12:47:22 +0800
From: pengdonglin <dolinux.peng@...il.com>
To: tj@...nel.org,
	tony.luck@...el.com,
	jani.nikula@...ux.intel.com,
	ap420073@...il.com,
	jv@...sburgh.net,
	freude@...ux.ibm.com,
	bcrl@...ck.org,
	trondmy@...nel.org,
	longman@...hat.com,
	kees@...nel.org
Cc: bigeasy@...utronix.de,
	hdanton@...a.com,
	paulmck@...nel.org,
	linux-kernel@...r.kernel.org,
	linux-rt-devel@...ts.linux.dev,
	linux-nfs@...r.kernel.org,
	linux-aio@...ck.org,
	linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	netdev@...r.kernel.org,
	intel-gfx@...ts.freedesktop.org,
	linux-wireless@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	linux-s390@...r.kernel.org,
	cgroups@...r.kernel.org,
	pengdonglin <dolinux.peng@...il.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	pengdonglin <pengdonglin@...omi.com>
Subject: [PATCH v3 01/14] ACPI: APEI: Remove redundant rcu_read_lock/unlock() in spin_lock

From: pengdonglin <pengdonglin@...omi.com>

Since commit a8bb74acd8efe ("rcu: Consolidate RCU-sched update-side function definitions")
there is no difference between rcu_read_lock(), rcu_read_lock_bh() and
rcu_read_lock_sched() in terms of RCU read section and the relevant grace
period. That means that spin_lock(), which implies rcu_read_lock_sched(),
also implies rcu_read_lock().

There is no need no explicitly start a RCU read section if one has already
been started implicitly by spin_lock().

Simplify the code and remove the inner rcu_read_lock() invocation.

Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Hanjun Guo <guohanjun@...wei.com>
Signed-off-by: pengdonglin <pengdonglin@...omi.com>
Signed-off-by: pengdonglin <dolinux.peng@...il.com>
---
 drivers/acpi/apei/ghes.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index a0d54993edb3..97ee19f2cae0 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -1207,12 +1207,10 @@ static int ghes_notify_hed(struct notifier_block *this, unsigned long event,
 	int ret = NOTIFY_DONE;
 
 	spin_lock_irqsave(&ghes_notify_lock_irq, flags);
-	rcu_read_lock();
 	list_for_each_entry_rcu(ghes, &ghes_hed, list) {
 		if (!ghes_proc(ghes))
 			ret = NOTIFY_OK;
 	}
-	rcu_read_unlock();
 	spin_unlock_irqrestore(&ghes_notify_lock_irq, flags);
 
 	return ret;
-- 
2.34.1