This patch set deliberately targets net-next and lacks Fixes: tags due
to caution on my part.
While testing some SFP modules on the Solidrun Honeycomb LX2K platform,
I noticed that rebooting causes a deadlock:
============================================
WARNING: possible recursive locking detected
6.1.0-rc5-07010-ga9b9500ffaac-dirty #656 Not tainted
--------------------------------------------
systemd-shutdow/1 is trying to acquire lock:
ffffa62db6cf42f0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x1c/0x30
but task is already holding lock:
ffffa62db6cf42f0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x1c/0x30
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(rtnl_mutex);
lock(rtnl_mutex);
*** DEADLOCK ***
May be due to missing lock nesting notation
6 locks held by systemd-shutdow/1:
#0: ffffa62db6863c70 (system_transition_mutex){+.+.}-{4:4}, at: __do_sys_reboot+0xd4/0x260
#1: ffff2f2b0176f100 (&dev->mutex){....}-{4:4}, at: device_shutdown+0xf4/0x260
#2: ffff2f2b017be900 (&dev->mutex){....}-{4:4}, at: device_shutdown+0x104/0x260
#3: ffff2f2b017680f0 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0x40/0x260
#4: ffff2f2b0e1608f0 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0x40/0x260
#5: ffffa62db6cf42f0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x1c/0x30
stack backtrace:
CPU: 6 PID: 1 Comm: systemd-shutdow Not tainted 6.1.0-rc5-07010-ga9b9500ffaac-dirty #656
Hardware name: SolidRun LX2160A Honeycomb (DT)
Call trace:
lock_acquire+0x68/0x84
__mutex_lock+0x98/0x460
mutex_lock_nested+0x2c/0x40
rtnl_lock+0x1c/0x30
sfp_bus_del_upstream+0x1c/0xac
phylink_destroy+0x1c/0x50
dpaa2_mac_disconnect+0x28/0x70
dpaa2_eth_remove+0x1dc/0x1f0
fsl_mc_driver_remove+0x24/0x60
device_remove+0x70/0x80
device_release_driver_internal+0x1f0/0x260
device_links_unbind_consumers+0xe0/0x110
device_release_driver_internal+0x138/0x260
device_release_driver+0x18/0x24
bus_remove_device+0x12c/0x13c
device_del+0x16c/0x424
fsl_mc_device_remove+0x28/0x40
__fsl_mc_device_remove+0x10/0x20
device_for_each_child+0x5c/0xac
dprc_remove+0x94/0xb4
fsl_mc_driver_remove+0x24/0x60
device_remove+0x70/0x80
device_release_driver_internal+0x1f0/0x260
device_release_driver+0x18/0x24
bus_remove_device+0x12c/0x13c
device_del+0x16c/0x424
fsl_mc_bus_remove+0x8c/0x10c
fsl_mc_bus_shutdown+0x10/0x20
platform_shutdown+0x24/0x3c
device_shutdown+0x15c/0x260
kernel_restart+0x40/0xa4
__do_sys_reboot+0x1e4/0x260
__arm64_sys_reboot+0x24/0x30
But fixing this appears to be not so simple. The patch set represents my
attempt to address it.
In short, the problem is that dpaa2_mac_connect() and dpaa2_mac_disconnect()
call 2 phylink functions in a row, one takes rtnl_lock() itself -
phylink_create(), and one which requires rtnl_lock() to be held by the
caller - phylink_fwnode_phy_connect(). The existing approach in the
drivers is too simple. We take rtnl_lock() when calling dpaa2_mac_connect(),
which is what results in the deadlock.
Fixing just that creates another problem. The drivers make use of
rtnl_lock() for serializing with other code paths too. I think I've
found all those code paths, and established other mechanisms for
serializing with them.
Vladimir Oltean (12):
net: dpaa2-eth: don't use -ENOTSUPP error code
net: dpaa2: replace dpaa2_mac_is_type_fixed() with
dpaa2_mac_is_type_phy()
net: dpaa2-mac: absorb phylink_start() call into dpaa2_mac_start()
net: dpaa2-mac: remove defensive check in dpaa2_mac_disconnect()
net: dpaa2-eth: assign priv->mac after dpaa2_mac_connect() call
net: dpaa2-switch: assign port_priv->mac after dpaa2_mac_connect()
call
net: dpaa2: publish MAC stringset to ethtool -S even if MAC is missing
net: dpaa2-switch replace direct MAC access with
dpaa2_switch_port_has_mac()
net: dpaa2-eth: connect to MAC before requesting the "endpoint
changed" IRQ
net: dpaa2-eth: serialize changes to priv->mac with a mutex
net: dpaa2-switch: serialize changes to priv->mac with a mutex
net: dpaa2-mac: move rtnl_lock() only around
phylink_{,dis}connect_phy()
.../freescale/dpaa2/mac-phy-support.rst | 9 +-
.../net/ethernet/freescale/dpaa2/dpaa2-eth.c | 87 ++++++++++++-------
.../net/ethernet/freescale/dpaa2/dpaa2-eth.h | 11 +--
.../ethernet/freescale/dpaa2/dpaa2-ethtool.c | 70 ++++++++++-----
.../net/ethernet/freescale/dpaa2/dpaa2-mac.c | 16 +++-
.../net/ethernet/freescale/dpaa2/dpaa2-mac.h | 10 ++-
.../freescale/dpaa2/dpaa2-switch-ethtool.c | 45 ++++++----
.../ethernet/freescale/dpaa2/dpaa2-switch.c | 59 +++++++++----
.../ethernet/freescale/dpaa2/dpaa2-switch.h | 9 +-
9 files changed, 212 insertions(+), 104 deletions(-)
--
2.34.1
