6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Yishai Hadas yishaih@nvidia.com
[ Upstream commit 1b10a519a45704d4b06ebd9245b272d145752c18 ]
Fix a lockdep warning [1] observed during the write combining test.
The warning indicates a potential nested lock scenario that could lead to a deadlock.
However, this is a false positive alarm because the SF lock and its parent lock are distinct ones.
The lockdep confusion arises because the locks belong to the same object class (i.e., struct mlx5_core_dev).
To resolve this, the code has been refactored to avoid taking both locks. Instead, only the parent lock is acquired.
[1] raw_ethernet_bw/2118 is trying to acquire lock: [ 213.619032] ffff88811dd75e08 (&dev->wc_state_lock){+.+.}-{3:3}, at: mlx5_wc_support_get+0x18c/0x210 [mlx5_core] [ 213.620270] [ 213.620270] but task is already holding lock: [ 213.620943] ffff88810b585e08 (&dev->wc_state_lock){+.+.}-{3:3}, at: mlx5_wc_support_get+0x10c/0x210 [mlx5_core] [ 213.622045] [ 213.622045] other info that might help us debug this: [ 213.622778] Possible unsafe locking scenario: [ 213.622778] [ 213.623465] CPU0 [ 213.623815] ---- [ 213.624148] lock(&dev->wc_state_lock); [ 213.624615] lock(&dev->wc_state_lock); [ 213.625071] [ 213.625071] *** DEADLOCK *** [ 213.625071] [ 213.625805] May be due to missing lock nesting notation [ 213.625805] [ 213.626522] 4 locks held by raw_ethernet_bw/2118: [ 213.627019] #0: ffff88813f80d578 (&uverbs_dev->disassociate_srcu){.+.+}-{0:0}, at: ib_uverbs_ioctl+0xc4/0x170 [ib_uverbs] [ 213.628088] #1: ffff88810fb23930 (&file->hw_destroy_rwsem){.+.+}-{3:3}, at: ib_init_ucontext+0x2d/0xf0 [ib_uverbs] [ 213.629094] #2: ffff88810fb23878 (&file->ucontext_lock){+.+.}-{3:3}, at: ib_init_ucontext+0x49/0xf0 [ib_uverbs] [ 213.630106] #3: ffff88810b585e08 (&dev->wc_state_lock){+.+.}-{3:3}, at: mlx5_wc_support_get+0x10c/0x210 [mlx5_core] [ 213.631185] [ 213.631185] stack backtrace: [ 213.631718] CPU: 1 UID: 0 PID: 2118 Comm: raw_ethernet_bw Not tainted 6.12.0-rc7_internal_net_next_mlx5_89a0ad0 #1 [ 213.632722] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 [ 213.633785] Call Trace: [ 213.634099] [ 213.634393] dump_stack_lvl+0x7e/0xc0 [ 213.634806] print_deadlock_bug+0x278/0x3c0 [ 213.635265] __lock_acquire+0x15f4/0x2c40 [ 213.635712] lock_acquire+0xcd/0x2d0 [ 213.636120] ? mlx5_wc_support_get+0x18c/0x210 [mlx5_core] [ 213.636722] ? mlx5_ib_enable_lb+0x24/0xa0 [mlx5_ib] [ 213.637277] __mutex_lock+0x81/0xda0 [ 213.637697] ? mlx5_wc_support_get+0x18c/0x210 [mlx5_core] [ 213.638305] ? mlx5_wc_support_get+0x18c/0x210 [mlx5_core] [ 213.638902] ? rcu_read_lock_sched_held+0x3f/0x70 [ 213.639400] ? mlx5_wc_support_get+0x18c/0x210 [mlx5_core] [ 213.640016] mlx5_wc_support_get+0x18c/0x210 [mlx5_core] [ 213.640615] set_ucontext_resp+0x68/0x2b0 [mlx5_ib] [ 213.641144] ? debug_mutex_init+0x33/0x40 [ 213.641586] mlx5_ib_alloc_ucontext+0x18e/0x7b0 [mlx5_ib] [ 213.642145] ib_init_ucontext+0xa0/0xf0 [ib_uverbs] [ 213.642679] ib_uverbs_handler_UVERBS_METHOD_GET_CONTEXT+0x95/0xc0 [ib_uverbs] [ 213.643426] ? _copy_from_user+0x46/0x80 [ 213.643878] ib_uverbs_cmd_verbs+0xa6b/0xc80 [ib_uverbs] [ 213.644426] ? ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x130/0x130 [ib_uverbs] [ 213.645213] ? __lock_acquire+0xa99/0x2c40 [ 213.645675] ? lock_acquire+0xcd/0x2d0 [ 213.646101] ? ib_uverbs_ioctl+0xc4/0x170 [ib_uverbs] [ 213.646625] ? reacquire_held_locks+0xcf/0x1f0 [ 213.647102] ? do_user_addr_fault+0x45d/0x770 [ 213.647586] ib_uverbs_ioctl+0xe0/0x170 [ib_uverbs] [ 213.648102] ? ib_uverbs_ioctl+0xc4/0x170 [ib_uverbs] [ 213.648632] __x64_sys_ioctl+0x4d3/0xaa0 [ 213.649060] ? do_user_addr_fault+0x4a8/0x770 [ 213.649528] do_syscall_64+0x6d/0x140 [ 213.649947] entry_SYSCALL_64_after_hwframe+0x4b/0x53 [ 213.650478] RIP: 0033:0x7fa179b0737b [ 213.650893] Code: ff ff ff 85 c0 79 9b 49 c7 c4 ff ff ff ff 5b 5d 4c 89 e0 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 7d 2a 0f 00 f7 d8 64 89 01 48 [ 213.652619] RSP: 002b:00007ffd2e6d46e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [ 213.653390] RAX: ffffffffffffffda RBX: 00007ffd2e6d47f8 RCX: 00007fa179b0737b [ 213.654084] RDX: 00007ffd2e6d47e0 RSI: 00000000c0181b01 RDI: 0000000000000003 [ 213.654767] RBP: 00007ffd2e6d47c0 R08: 00007fa1799be010 R09: 0000000000000002 [ 213.655453] R10: 00007ffd2e6d4960 R11: 0000000000000246 R12: 00007ffd2e6d487c [ 213.656170] R13: 0000000000000027 R14: 0000000000000001 R15: 00007ffd2e6d4f70
Fixes: d98995b4bf98 ("net/mlx5: Reimplement write combining test") Signed-off-by: Yishai Hadas yishaih@nvidia.com Reviewed-by: Michael Guralnik michaelgur@nvidia.com Reviewed-by: Larysa Zaremba larysa.zaremba@intel.com Signed-off-by: Tariq Toukan tariqt@nvidia.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/mellanox/mlx5/core/wc.c | 24 ++++++++++---------- 1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/wc.c b/drivers/net/ethernet/mellanox/mlx5/core/wc.c index 1bed75eca97db..740b719e7072d 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/wc.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/wc.c @@ -382,6 +382,7 @@ static void mlx5_core_test_wc(struct mlx5_core_dev *mdev)
bool mlx5_wc_support_get(struct mlx5_core_dev *mdev) { + struct mutex *wc_state_lock = &mdev->wc_state_lock; struct mlx5_core_dev *parent = NULL;
if (!MLX5_CAP_GEN(mdev, bf)) { @@ -400,32 +401,31 @@ bool mlx5_wc_support_get(struct mlx5_core_dev *mdev) */ goto out;
- mutex_lock(&mdev->wc_state_lock); - - if (mdev->wc_state != MLX5_WC_STATE_UNINITIALIZED) - goto unlock; - #ifdef CONFIG_MLX5_SF - if (mlx5_core_is_sf(mdev)) + if (mlx5_core_is_sf(mdev)) { parent = mdev->priv.parent_mdev; + wc_state_lock = &parent->wc_state_lock; + } #endif
- if (parent) { - mutex_lock(&parent->wc_state_lock); + mutex_lock(wc_state_lock);
+ if (mdev->wc_state != MLX5_WC_STATE_UNINITIALIZED) + goto unlock; + + if (parent) { mlx5_core_test_wc(parent);
mlx5_core_dbg(mdev, "parent set wc_state=%d\n", parent->wc_state); mdev->wc_state = parent->wc_state;
- mutex_unlock(&parent->wc_state_lock); + } else { + mlx5_core_test_wc(mdev); }
- mlx5_core_test_wc(mdev); - unlock: - mutex_unlock(&mdev->wc_state_lock); + mutex_unlock(wc_state_lock); out: mlx5_core_dbg(mdev, "wc_state=%d\n", mdev->wc_state);