[PATCH AUTOSEL 5.18 68/93] net: devlink: avoid false DEADLOCK warning reported by lockdep

Sasha Levin
2022-08-11T16:07:39Z

From: Moshe Shemesh <moshe@nvidia.com>

[ Upstream commit e26fde2f5befad0951fe6345403616bf51e901be ]

Add a lock_class_key per devlink instance to avoid DEADLOCK warning by
lockdep, while locking more than one devlink instance in driver code,
for example in opening VFs flow.

Kernel log:
[ 101.433802] ============================================
[ 101.433803] WARNING: possible recursive locking detected
[ 101.433810] 5.19.0-rc1+ #35 Not tainted
[ 101.433812] --------------------------------------------
[ 101.433813] bash/892 is trying to acquire lock:
[ 101.433815] ffff888127bfc2f8 (&devlink->lock){+.+.}-{3:3}, at: probe_one+0x3c/0x690 [mlx5_core]
[ 101.433909]
but task is already holding lock:
[ 101.433910] ffff888118f4c2f8 (&devlink->lock){+.+.}-{3:3}, at: mlx5_core_sriov_configure+0x62/0x280 [mlx5_core]
[ 101.433989]
other info that might help us debug this:
[ 101.433990] Possible unsafe locking scenario:

[ 101.433991] CPU0
[ 101.433991] ----
[ 101.433992] lock(&devlink->lock);
[ 101.433993] lock(&devlink->lock);
[ 101.433995]
*** DEADLOCK ***

[ 101.433996] May be due to missing lock nesting notation

[ 101.433996] 6 locks held by bash/892:
[ 101.433998] #0: ffff88810eb50448 (sb_writers#3){.+.+}-{0:0}, at: ksys_write+0xf3/0x1d0
[ 101.434009] #1: ffff888114777c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x20d/0x520
[ 101.434017] #2: ffff888102b58660 (kn->active#231){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x230/0x520
[ 101.434023] #3: ffff888102d70198 (&dev->mutex){....}-{3:3}, at: sriov_numvfs_store+0x132/0x310
[ 101.434031] #4: ffff888118f4c2f8 (&devlink->lock){+.+.}-{3:3}, at: mlx5_core_sriov_configure+0x62/0x280 [mlx5_core]
[ 101.434108] #5: ffff88812adce198 (&dev->mutex){....}-{3:3}, at: __device_attach+0x76/0x430
[ 101.434116]
stack backtrace:
[ 101.434118] CPU: 5 PID: 892 Comm: bash Not tainted 5.19.0-rc1+ #35
[ 101.434120] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[ 101.434130] Call Trace:
[ 101.434133] <TASK>
[ 101.434135] dump_stack_lvl+0x57/0x7d
[ 101.434145] __lock_acquire.cold+0x1df/0x3e7
[ 101.434151] ? register_lock_class+0x1880/0x1880
[ 101.434157] lock_acquire+0x1c1/0x550
[ 101.434160] ? probe_one+0x3c/0x690 [mlx5_core]
[ 101.434229] ? lockdep_hardirqs_on_prepare+0x400/0x400
[ 101.434232] ? __xa_alloc+0x1ed/0x2d0
[ 101.434236] ? ksys_write+0xf3/0x1d0
[ 101.434239] __mutex_lock+0x12c/0x14b0
[ 101.434243] ? probe_one+0x3c/0x690 [mlx5_core]
[ 101.434312] ? probe_one+0x3c/0x690 [mlx5_core]
[ 101.434380] ? devlink_alloc_ns+0x11b/0x910
[ 101.434385] ? mutex_lock_io_nested+0x1320/0x1320
[ 101.434388] ? lockdep_init_map_type+0x21a/0x7d0
[ 101.434391] ? lockdep_init_map_type+0x21a/0x7d0
[ 101.434393] ? __init_swait_queue_head+0x70/0xd0
[ 101.434397] probe_one+0x3c/0x690 [mlx5_core]
[ 101.434467] pci_device_probe+0x1b4/0x480
[ 101.434471] really_probe+0x1e0/0xaa0
[ 101.434474] __driver_probe_device+0x219/0x480
[ 101.434478] driver_probe_device+0x49/0x130
[ 101.434481] __device_attach_driver+0x1b8/0x280
[ 101.434484] ? driver_allows_async_probing+0x140/0x140
[ 101.434487] bus_for_each_drv+0x123/0x1a0
[ 101.434489] ? bus_for_each_dev+0x1a0/0x1a0
[ 101.434491] ? lockdep_hardirqs_on_prepare+0x286/0x400
[ 101.434494] ? trace_hardirqs_on+0x2d/0x100
[ 101.434498] __device_attach+0x1a3/0x430
[ 101.434501] ? device_driver_attach+0x1e0/0x1e0
[ 101.434503] ? pci_bridge_d3_possible+0x1e0/0x1e0
[ 101.434506] ? pci_create_resource_files+0xeb/0x190
[ 101.434511] pci_bus_add_device+0x6c/0xa0
[ 101.434514] pci_iov_add_virtfn+0x9e4/0xe00
[ 101.434517] ? trace_hardirqs_on+0x2d/0x100
[ 101.434521] sriov_enable+0x64a/0xca0
[ 101.434524] ? pcibios_sriov_disable+0x10/0x10
[ 101.434528] mlx5_core_sriov_configure+0xab/0x280 [mlx5_core]
[ 101.434602] sriov_numvfs_store+0x20a/0x310
[ 101.434605] ? sriov_totalvfs_show+0xc0/0xc0
[ 101.434608] ? sysfs_file_ops+0x170/0x170
[ 101.434611] ? sysfs_file_ops+0x117/0x170
[ 101.434614] ? sysfs_file_ops+0x170/0x170
[ 101.434616] kernfs_fop_write_iter+0x348/0x520
[ 101.434619] new_sync_write+0x2e5/0x520
[ 101.434621] ? new_sync_read+0x520/0x520
[ 101.434624] ? lock_acquire+0x1c1/0x550
[ 101.434626] ? lockdep_hardirqs_on_prepare+0x400/0x400
[ 101.434630] vfs_write+0x5cb/0x8d0
[ 101.434633] ksys_write+0xf3/0x1d0
[ 101.434635] ? __x64_sys_read+0xb0/0xb0
[ 101.434638] ? lockdep_hardirqs_on_prepare+0x286/0x400
[ 101.434640] ? syscall_enter_from_user_mode+0x1d/0x50
[ 101.434643] do_syscall_64+0x3d/0x90
[ 101.434647] entry_SYSCALL_64_after_hwframe+0x46/0xb0
[ 101.434650] RIP: 0033:0x7f5ff536b2f7
[ 101.434658] Code: 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f
1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f
05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
[ 101.434661] RSP: 002b:00007ffd9ea85d58 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 101.434664] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f5ff536b2f7
[ 101.434666] RDX: 0000000000000002 RSI: 000055c4c279e230 RDI: 0000000000000001
[ 101.434668] RBP: 000055c4c279e230 R08: 000000000000000a R09: 0000000000000001
[ 101.434669] R10: 000055c4c283cbf0 R11: 0000000000000246 R12: 0000000000000002
[ 101.434670] R13: 00007f5ff543d500 R14: 0000000000000002 R15: 00007f5ff543d700
[ 101.434673] </TASK>

Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/devlink.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index aeca13b6e57b..2c665396a707 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -64,6 +64,7 @@ struct devlink {
* port, sb, dpipe, resource, params, region, traps and more.
*/
struct mutex lock;
+ struct lock_class_key lock_key;
u8 reload_failed:1;
refcount_t refcount;
struct completion comp;
@@ -9052,7 +9053,9 @@ struct devlink *devlink_alloc_ns(const struct devlink_ops *ops,
INIT_LIST_HEAD(&devlink->trap_list);
INIT_LIST_HEAD(&devlink->trap_group_list);
INIT_LIST_HEAD(&devlink->trap_policer_list);
+ lockdep_register_key(&devlink->lock_key);
mutex_init(&devlink->lock);
+ lockdep_set_class(&devlink->lock, &devlink->lock_key);
mutex_init(&devlink->reporters_lock);
refcount_set(&devlink->refcount, 1);
init_completion(&devlink->comp);
@@ -9193,6 +9196,7 @@ void devlink_free(struct devlink *devlink)

mutex_destroy(&devlink->reporters_lock);
mutex_destroy(&devlink->lock);
+ lockdep_unregister_key(&devlink->lock_key);
WARN_ON(!list_empty(&devlink->trap_policer_list));
WARN_ON(!list_empty(&devlink->trap_group_list));
WARN_ON(!list_empty(&devlink->trap_list));
--
2.35.1