netdev - [PATCH net v2] net: xdp: don't call notifiers during driver init

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Message-Id: <20230316220234.598091-1-kuba@kernel.org>
Date:   Thu, 16 Mar 2023 15:02:34 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, pabeni@...hat.com,
        Jakub Kicinski <kuba@...nel.org>, ast@...nel.org,
        daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com,
        lorenzo@...nel.org, tariqt@...dia.com, bpf@...r.kernel.org
Subject: [PATCH net v2] net: xdp: don't call notifiers during driver init

Drivers will commonly perform feature setting during init, if they use
the xdp_set_features_flag() helper they'll likely run into an ASSERT_RTNL()
inside call_netdevice_notifiers_info().

Don't call the notifier until the device is actually registered.
Nothing should be tracking the device until its registered and
after its unregistration has started.

Fixes: 4d5ab0ad964d ("net/mlx5e: take into account device reconfiguration for xdp_features flag")
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
v2: only call for REGISTERED devices, not dead ones
v1: https://lore.kernel.org/all/20230316002903.492497-1-kuba@kernel.org/

CC: ast@...nel.org
CC: daniel@...earbox.net
CC: hawk@...nel.org
CC: john.fastabend@...il.com
CC: lorenzo@...nel.org
CC: tariqt@...dia.com
CC: bpf@...r.kernel.org
---
 net/core/xdp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/xdp.c b/net/core/xdp.c
index 87e654b7d06c..b5737e47ec41 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -781,7 +781,9 @@ void xdp_set_features_flag(struct net_device *dev, xdp_features_t val)
 		return;
 
 	dev->xdp_features = val;
-	call_netdevice_notifiers(NETDEV_XDP_FEAT_CHANGE, dev);
+
+	if (dev->reg_state == NETREG_REGISTERED)
+		call_netdevice_notifiers(NETDEV_XDP_FEAT_CHANGE, dev);
 }
 EXPORT_SYMBOL_GPL(xdp_set_features_flag);
 
-- 
2.39.2