[PATCH v3 11/14] net: ncsi: Remove redundant rcu_read_lock/unlock() in spin_lock

pengdonglin posted 14 patches 2 weeks, 2 days ago
[PATCH v3 11/14] net: ncsi: Remove redundant rcu_read_lock/unlock() in spin_lock
Posted by pengdonglin 2 weeks, 2 days ago
From: pengdonglin <pengdonglin@xiaomi.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: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Cc: Paul Fertser <fercerpav@gmail.com>
Signed-off-by: pengdonglin <pengdonglin@xiaomi.com>
Signed-off-by: pengdonglin <dolinux.peng@gmail.com>
---
 net/ncsi/ncsi-manage.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/ncsi/ncsi-manage.c b/net/ncsi/ncsi-manage.c
index 446e4e3b9553..6e36cd64a31e 100644
--- a/net/ncsi/ncsi-manage.c
+++ b/net/ncsi/ncsi-manage.c
@@ -650,7 +650,6 @@ static int set_one_vid(struct ncsi_dev_priv *ndp, struct ncsi_channel *nc,
 
 	spin_lock_irqsave(&nc->lock, flags);
 
-	rcu_read_lock();
 	list_for_each_entry_rcu(vlan, &ndp->vlan_vids, list) {
 		vid = vlan->vid;
 		for (i = 0; i < ncf->n_vids; i++)
@@ -661,7 +660,6 @@ static int set_one_vid(struct ncsi_dev_priv *ndp, struct ncsi_channel *nc,
 		if (vid)
 			break;
 	}
-	rcu_read_unlock();
 
 	if (!vid) {
 		/* No VLAN ID is not set */
-- 
2.34.1
Re: [PATCH v3 11/14] net: ncsi: Remove redundant rcu_read_lock/unlock() in spin_lock
Posted by Paul Fertser 2 weeks, 2 days ago
Hello pengdonglin,

Thank you for the patch, looks reasonable and justified.

On Tue, Sep 16, 2025 at 12:47:32PM +0800, pengdonglin wrote:
> From: pengdonglin <pengdonglin@xiaomi.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.

Reviewed-by: Paul Fertser <fercerpav@gmail.com>