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Date: Fri, 03 Mar 2023 16:37:54 +0000
From: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
To: Andrew Lunn <andrew@...n.ch>,
Heiner Kallweit <hkallweit1@...il.com>
Cc: Marc Zyngier <maz@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Subject: [PATCH net] net: phylib: get rid of unnecessary locking
The locking in phy_probe() and phy_remove() does very little to prevent
any races with e.g. phy_attach_direct(), but instead causes lockdep ABBA
warnings. Remove it.
======================================================
WARNING: possible circular locking dependency detected
6.2.0-dirty #1108 Tainted: G W E
------------------------------------------------------
ip/415 is trying to acquire lock:
ffff5c268f81ef50 (&dev->lock){+.+.}-{3:3}, at: phy_attach_direct+0x17c/0x3a0 [libphy]
but task is already holding lock:
ffffaef6496cb518 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x154/0x560
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (rtnl_mutex){+.+.}-{3:3}:
__lock_acquire+0x35c/0x6c0
lock_acquire.part.0+0xcc/0x220
lock_acquire+0x68/0x84
__mutex_lock+0x8c/0x414
mutex_lock_nested+0x34/0x40
rtnl_lock+0x24/0x30
sfp_bus_add_upstream+0x34/0x150
phy_sfp_probe+0x4c/0x94 [libphy]
mv3310_probe+0x148/0x184 [marvell10g]
phy_probe+0x8c/0x200 [libphy]
call_driver_probe+0xbc/0x15c
really_probe+0xc0/0x320
__driver_probe_device+0x84/0x120
driver_probe_device+0x44/0x120
__device_attach_driver+0xc4/0x160
bus_for_each_drv+0x80/0xe0
__device_attach+0xb0/0x1f0
device_initial_probe+0x1c/0x2c
bus_probe_device+0xa4/0xb0
device_add+0x360/0x53c
phy_device_register+0x60/0xa4 [libphy]
fwnode_mdiobus_phy_device_register+0xc0/0x190 [fwnode_mdio]
fwnode_mdiobus_register_phy+0x160/0xd80 [fwnode_mdio]
of_mdiobus_register+0x140/0x340 [of_mdio]
orion_mdio_probe+0x298/0x3c0 [mvmdio]
platform_probe+0x70/0xe0
call_driver_probe+0x34/0x15c
really_probe+0xc0/0x320
__driver_probe_device+0x84/0x120
driver_probe_device+0x44/0x120
__driver_attach+0x104/0x210
bus_for_each_dev+0x78/0xdc
driver_attach+0x2c/0x3c
bus_add_driver+0x184/0x240
driver_register+0x80/0x13c
__platform_driver_register+0x30/0x3c
xt_compat_calc_jump+0x28/0xa4 [x_tables]
do_one_initcall+0x50/0x1b0
do_init_module+0x50/0x1fc
load_module+0x684/0x744
__do_sys_finit_module+0xc4/0x140
__arm64_sys_finit_module+0x28/0x34
invoke_syscall+0x50/0x120
el0_svc_common.constprop.0+0x6c/0x1b0
do_el0_svc+0x34/0x44
el0_svc+0x48/0xf0
el0t_64_sync_handler+0xb8/0xc0
el0t_64_sync+0x1a0/0x1a4
-> #0 (&dev->lock){+.+.}-{3:3}:
check_prev_add+0xb4/0xc80
validate_chain+0x414/0x47c
__lock_acquire+0x35c/0x6c0
lock_acquire.part.0+0xcc/0x220
lock_acquire+0x68/0x84
__mutex_lock+0x8c/0x414
mutex_lock_nested+0x34/0x40
phy_attach_direct+0x17c/0x3a0 [libphy]
phylink_fwnode_phy_connect.part.0+0x70/0xe4 [phylink]
phylink_fwnode_phy_connect+0x48/0x60 [phylink]
mvpp2_open+0xec/0x2e0 [mvpp2]
__dev_open+0x104/0x214
__dev_change_flags+0x1d4/0x254
dev_change_flags+0x2c/0x7c
do_setlink+0x254/0xa50
__rtnl_newlink+0x430/0x514
rtnl_newlink+0x58/0x8c
rtnetlink_rcv_msg+0x17c/0x560
netlink_rcv_skb+0x64/0x150
rtnetlink_rcv+0x20/0x30
netlink_unicast+0x1d4/0x2b4
netlink_sendmsg+0x1a4/0x400
____sys_sendmsg+0x228/0x290
___sys_sendmsg+0x88/0xec
__sys_sendmsg+0x70/0xd0
__arm64_sys_sendmsg+0x2c/0x40
invoke_syscall+0x50/0x120
el0_svc_common.constprop.0+0x6c/0x1b0
do_el0_svc+0x34/0x44
el0_svc+0x48/0xf0
el0t_64_sync_handler+0xb8/0xc0
el0t_64_sync+0x1a0/0x1a4
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(rtnl_mutex);
lock(&dev->lock);
lock(rtnl_mutex);
lock(&dev->lock);
*** DEADLOCK ***
Fixes: 298e54fa810e ("net: phy: add core phylib sfp support")
Reported-by: Marc Zyngier <maz@...nel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
drivers/net/phy/phy_device.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 9e9fd8ff00f6..1785f1cead97 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -3098,8 +3098,6 @@ static int phy_probe(struct device *dev)
if (phydrv->flags & PHY_IS_INTERNAL)
phydev->is_internal = true;
- mutex_lock(&phydev->lock);
-
/* Deassert the reset signal */
phy_device_reset(phydev, 0);
@@ -3188,12 +3186,10 @@ static int phy_probe(struct device *dev)
phydev->state = PHY_READY;
out:
- /* Assert the reset signal */
+ /* Re-assert the reset signal on error */
if (err)
phy_device_reset(phydev, 1);
- mutex_unlock(&phydev->lock);
-
return err;
}
@@ -3203,9 +3199,7 @@ static int phy_remove(struct device *dev)
cancel_delayed_work_sync(&phydev->state_queue);
- mutex_lock(&phydev->lock);
phydev->state = PHY_DOWN;
- mutex_unlock(&phydev->lock);
sfp_bus_del_upstream(phydev->sfp_bus);
phydev->sfp_bus = NULL;
--
2.30.2
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