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dsa: qca8k: Use nested lock to avoid splat

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BugLink: https://bugs.launchpad.net/bugs/2102118

[ Upstream commit 078e0d596f7b5952dad8662ace8f20ed2165e2ce ]

qca8k_phy_eth_command() is used to probe the child MDIO bus while the
parent MDIO is locked. This causes lockdep splat, reporting a possible
deadlock. It is not an actually deadlock, because different locks are
used. By making use of mutex_lock_nested() we can avoid this false
positive.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241110175955.3053664-1-andrew@lunn.ch
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
This commit is contained in:
Andrew Lunn
2025-03-12 22:51:00 +09:00
committed by Stefan Bader
parent cb6552b982
commit 4d741663b6
1 changed files with 1 additions and 1 deletions
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drivers/net/dsa/qca/qca8k-8xxx.c
+1 -1
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@@ -673,7 +673,7 @@ qca8k_phy_eth_command(struct qca8k_priv *priv, bool read, int phy,
* We therefore need to lock the MDIO bus onto which the switch is
* connected.
*/
mutex_lock(&priv->bus->mdio_lock);
mutex_lock_nested(&priv->bus->mdio_lock, MDIO_MUTEX_NESTED);
/* Actually start the request:
* 1. Send mdio master packet