[PATCH net-next v1 10/21] net/mlx5: Accept devlink user input after driver initialization complete

From: Leon Romanovsky
Date: Sat Sep 25 2021 - 07:24:05 EST

From: Leon Romanovsky <leonro@xxxxxxxxxx>

The change of devlink_alloc() to accept device makes sure that device
is fully initialized and device_register() does nothing except allowing
users to use that devlink instance.

Such change ensures that no user input will be usable till that point and
it eliminates the need to worry about internal locking as long as devlink_register
is called last since all accesses to the devlink are during initialization.

This change fixes the following lockdep warning.

======================================================
WARNING: possible circular locking dependency detected
5.14.0-rc2+ #27 Not tainted
------------------------------------------------------
devlink/265 is trying to acquire lock:
ffff8880133c2bc0 (&dev->intf_state_mutex){+.+.}-{3:3}, at: mlx5_unload_one+0x1e/0xa0 [mlx5_core]
but task is already holding lock:
ffffffff8362b468 (devlink_mutex){+.+.}-{3:3}, at: devlink_nl_pre_doit+0x2b/0x8d0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:

-> #1 (devlink_mutex){+.+.}-{3:3}:
__mutex_lock+0x149/0x1310
devlink_register+0xe7/0x280
mlx5_devlink_register+0x118/0x480 [mlx5_core]
mlx5_init_one+0x34b/0x440 [mlx5_core]
probe_one+0x480/0x6e0 [mlx5_core]
pci_device_probe+0x2a0/0x4a0
really_probe+0x1cb/0xba0
__driver_probe_device+0x18f/0x470
driver_probe_device+0x49/0x120
__driver_attach+0x1ce/0x400
bus_for_each_dev+0x11e/0x1a0
bus_add_driver+0x309/0x570
driver_register+0x20f/0x390
0xffffffffa04a0062
do_one_initcall+0xd5/0x400
do_init_module+0x1c8/0x760
load_module+0x7d9d/0xa4b0
__do_sys_finit_module+0x118/0x1a0
do_syscall_64+0x3d/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (&dev->intf_state_mutex){+.+.}-{3:3}:
__lock_acquire+0x2999/0x5a40
lock_acquire+0x1a9/0x4a0
__mutex_lock+0x149/0x1310
mlx5_unload_one+0x1e/0xa0 [mlx5_core]
mlx5_devlink_reload_down+0x185/0x2b0 [mlx5_core]
devlink_reload+0x1f2/0x640
devlink_nl_cmd_reload+0x6c3/0x10d0
genl_family_rcv_msg_doit+0x1e9/0x2f0
genl_rcv_msg+0x27f/0x4a0
netlink_rcv_skb+0x11e/0x340
genl_rcv+0x24/0x40
netlink_unicast+0x433/0x700
netlink_sendmsg+0x6fb/0xbe0
sock_sendmsg+0xb0/0xe0
__sys_sendto+0x192/0x240
__x64_sys_sendto+0xdc/0x1b0
do_syscall_64+0x3d/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(devlink_mutex);
lock(&dev->intf_state_mutex);
lock(devlink_mutex);
lock(&dev->intf_state_mutex);

*** DEADLOCK ***

3 locks held by devlink/265:
#0: ffffffff836371d0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40
#1: ffffffff83637288 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x31a/0x4a0
#2: ffffffff8362b468 (devlink_mutex){+.+.}-{3:3}, at: devlink_nl_pre_doit+0x2b/0x8d0

stack backtrace:
CPU: 0 PID: 265 Comm: devlink Not tainted 5.14.0-rc2+ #27
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
Call Trace:
dump_stack_lvl+0x45/0x59
check_noncircular+0x268/0x310
? print_circular_bug+0x460/0x460
? __kernel_text_address+0xe/0x30
? alloc_chain_hlocks+0x1e6/0x5a0
__lock_acquire+0x2999/0x5a40
? lockdep_hardirqs_on_prepare+0x3e0/0x3e0
? add_lock_to_list.constprop.0+0x6c/0x530
lock_acquire+0x1a9/0x4a0
? mlx5_unload_one+0x1e/0xa0 [mlx5_core]
? lock_release+0x6c0/0x6c0
? lockdep_hardirqs_on_prepare+0x3e0/0x3e0
? lock_is_held_type+0x98/0x110
__mutex_lock+0x149/0x1310
? mlx5_unload_one+0x1e/0xa0 [mlx5_core]
? lock_is_held_type+0x98/0x110
? mlx5_unload_one+0x1e/0xa0 [mlx5_core]
? find_held_lock+0x2d/0x110
? mutex_lock_io_nested+0x1160/0x1160
? mlx5_lag_is_active+0x72/0x90 [mlx5_core]
? lock_downgrade+0x6d0/0x6d0
? do_raw_spin_lock+0x12e/0x270
? rwlock_bug.part.0+0x90/0x90
? mlx5_unload_one+0x1e/0xa0 [mlx5_core]
mlx5_unload_one+0x1e/0xa0 [mlx5_core]
mlx5_devlink_reload_down+0x185/0x2b0 [mlx5_core]
? netlink_broadcast_filtered+0x308/0xac0
? mlx5_devlink_info_get+0x1f0/0x1f0 [mlx5_core]
? __build_skb_around+0x110/0x2b0
? __alloc_skb+0x113/0x2b0
devlink_reload+0x1f2/0x640
? devlink_unregister+0x1e0/0x1e0
? security_capable+0x51/0x90
devlink_nl_cmd_reload+0x6c3/0x10d0
? devlink_nl_cmd_get_doit+0x1e0/0x1e0
? devlink_nl_pre_doit+0x72/0x8d0
genl_family_rcv_msg_doit+0x1e9/0x2f0
? __lock_acquire+0x15e2/0x5a40
? genl_family_rcv_msg_attrs_parse.constprop.0+0x240/0x240
? mutex_lock_io_nested+0x1160/0x1160
? security_capable+0x51/0x90
genl_rcv_msg+0x27f/0x4a0
? genl_get_cmd+0x3c0/0x3c0
? lock_acquire+0x1a9/0x4a0
? devlink_nl_cmd_get_doit+0x1e0/0x1e0
? lock_release+0x6c0/0x6c0
netlink_rcv_skb+0x11e/0x340
? genl_get_cmd+0x3c0/0x3c0
? netlink_ack+0x930/0x930
genl_rcv+0x24/0x40
netlink_unicast+0x433/0x700
? netlink_attachskb+0x750/0x750
? __alloc_skb+0x113/0x2b0
netlink_sendmsg+0x6fb/0xbe0
? netlink_unicast+0x700/0x700
? netlink_unicast+0x700/0x700
sock_sendmsg+0xb0/0xe0
__sys_sendto+0x192/0x240
? __x64_sys_getpeername+0xb0/0xb0
? do_sys_openat2+0x10a/0x370
? down_write_nested+0x150/0x150
? do_user_addr_fault+0x215/0xd50
? __x64_sys_openat+0x11f/0x1d0
? __x64_sys_open+0x1a0/0x1a0
__x64_sys_sendto+0xdc/0x1b0
? syscall_enter_from_user_mode+0x1d/0x50
do_syscall_64+0x3d/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f50b50b6b3a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 f3 0f 1e fa 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 15 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 76 c3 0f 1f 44 00 00 55 48 83 ec 30 44 89 4c
RSP: 002b:00007fff6c0d3f38 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007f50b50b6b3a
RDX: 0000000000000038 RSI: 000055763ac08440 RDI: 0000000000000003
RBP: 000055763ac08410 R08: 00007f50b5192200 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 000055763ac08410 R15: 000055763ac08440
mlx5_core 0000:00:09.0: firmware version: 4.8.9999
mlx5_core 0000:00:09.0: 0.000 Gb/s available PCIe bandwidth (8.0 GT/s PCIe x255 link)
mlx5_core 0000:00:09.0 eth1: Link up

Fixes: a6f3b62386a0 ("net/mlx5: Move devlink registration before interfaces load")
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
---
drivers/net/ethernet/mellanox/mlx5/core/devlink.c | 9 ++-------
drivers/net/ethernet/mellanox/mlx5/core/main.c | 2 ++
drivers/net/ethernet/mellanox/mlx5/core/sf/dev/driver.c | 2 ++
3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/devlink.c b/drivers/net/ethernet/mellanox/mlx5/core/devlink.c
index b36f721625e4..d7576b6fa43b 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/devlink.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/devlink.c
@@ -793,11 +793,11 @@ int mlx5_devlink_register(struct devlink *devlink)
{
int err;

- devlink_register(devlink);
err = devlink_params_register(devlink, mlx5_devlink_params,
ARRAY_SIZE(mlx5_devlink_params));
if (err)
- goto params_reg_err;
+ return err;
+
mlx5_devlink_set_params_init_values(devlink);

err = mlx5_devlink_auxdev_params_register(devlink);
@@ -808,7 +808,6 @@ int mlx5_devlink_register(struct devlink *devlink)
if (err)
goto traps_reg_err;

- devlink_params_publish(devlink);
return 0;

traps_reg_err:
@@ -816,17 +815,13 @@ int mlx5_devlink_register(struct devlink *devlink)
auxdev_reg_err:
devlink_params_unregister(devlink, mlx5_devlink_params,
ARRAY_SIZE(mlx5_devlink_params));
-params_reg_err:
- devlink_unregister(devlink);
return err;
}

void mlx5_devlink_unregister(struct devlink *devlink)
{
- devlink_params_unpublish(devlink);
mlx5_devlink_traps_unregister(devlink);
mlx5_devlink_auxdev_params_unregister(devlink);
devlink_params_unregister(devlink, mlx5_devlink_params,
ARRAY_SIZE(mlx5_devlink_params));
- devlink_unregister(devlink);
}
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c b/drivers/net/ethernet/mellanox/mlx5/core/main.c
index 79482824c64f..92b08fa07efa 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
@@ -1537,6 +1537,7 @@ static int probe_one(struct pci_dev *pdev, const struct pci_device_id *id)
dev_err(&pdev->dev, "mlx5_crdump_enable failed with error code %d\n", err);

pci_save_state(pdev);
+ devlink_register(devlink);
if (!mlx5_core_is_mp_slave(dev))
devlink_reload_enable(devlink);
return 0;
@@ -1559,6 +1560,7 @@ static void remove_one(struct pci_dev *pdev)
struct devlink *devlink = priv_to_devlink(dev);

devlink_reload_disable(devlink);
+ devlink_unregister(devlink);
mlx5_crdump_disable(dev);
mlx5_drain_health_wq(dev);
mlx5_uninit_one(dev);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/sf/dev/driver.c b/drivers/net/ethernet/mellanox/mlx5/core/sf/dev/driver.c
index 052f48068dc1..3cf272fa2164 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/sf/dev/driver.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/sf/dev/driver.c
@@ -46,6 +46,7 @@ static int mlx5_sf_dev_probe(struct auxiliary_device *adev, const struct auxilia
mlx5_core_warn(mdev, "mlx5_init_one err=%d\n", err);
goto init_one_err;
}
+ devlink_register(devlink);
devlink_reload_enable(devlink);
return 0;

@@ -65,6 +66,7 @@ static void mlx5_sf_dev_remove(struct auxiliary_device *adev)

devlink = priv_to_devlink(sf_dev->mdev);
devlink_reload_disable(devlink);
+ devlink_unregister(devlink);
mlx5_uninit_one(sf_dev->mdev);
iounmap(sf_dev->mdev->iseg);
mlx5_mdev_uninit(sf_dev->mdev);
--
2.31.1