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    Subject[PATCH 5.19 034/158] net/mlx5: Avoid false positive lockdep warning by adding lock_class_key
    Date
    From: Moshe Shemesh <moshe@nvidia.com>

    [ Upstream commit d59b73a66e5e0682442b6d7b4965364e57078b80 ]

    Add a lock_class_key per mlx5 device to avoid a false positive
    "possible circular locking dependency" warning by lockdep, on flows
    which lock more than one mlx5 device, such as adding SF.

    kernel log:
    ======================================================
    WARNING: possible circular locking dependency detected
    5.19.0-rc8+ #2 Not tainted
    ------------------------------------------------------
    kworker/u20:0/8 is trying to acquire lock:
    ffff88812dfe0d98 (&dev->intf_state_mutex){+.+.}-{3:3}, at: mlx5_init_one+0x2e/0x490 [mlx5_core]

    but task is already holding lock:
    ffff888101aa7898 (&(&notifier->n_head)->rwsem){++++}-{3:3}, at: blocking_notifier_call_chain+0x5a/0x130

    which lock already depends on the new lock.

    the existing dependency chain (in reverse order) is:

    -> #1 (&(&notifier->n_head)->rwsem){++++}-{3:3}:
    down_write+0x90/0x150
    blocking_notifier_chain_register+0x53/0xa0
    mlx5_sf_table_init+0x369/0x4a0 [mlx5_core]
    mlx5_init_one+0x261/0x490 [mlx5_core]
    probe_one+0x430/0x680 [mlx5_core]
    local_pci_probe+0xd6/0x170
    work_for_cpu_fn+0x4e/0xa0
    process_one_work+0x7c2/0x1340
    worker_thread+0x6f6/0xec0
    kthread+0x28f/0x330
    ret_from_fork+0x1f/0x30

    -> #0 (&dev->intf_state_mutex){+.+.}-{3:3}:
    __lock_acquire+0x2fc7/0x6720
    lock_acquire+0x1c1/0x550
    __mutex_lock+0x12c/0x14b0
    mlx5_init_one+0x2e/0x490 [mlx5_core]
    mlx5_sf_dev_probe+0x29c/0x370 [mlx5_core]
    auxiliary_bus_probe+0x9d/0xe0
    really_probe+0x1e0/0xaa0
    __driver_probe_device+0x219/0x480
    driver_probe_device+0x49/0x130
    __device_attach_driver+0x1b8/0x280
    bus_for_each_drv+0x123/0x1a0
    __device_attach+0x1a3/0x460
    bus_probe_device+0x1a2/0x260
    device_add+0x9b1/0x1b40
    __auxiliary_device_add+0x88/0xc0
    mlx5_sf_dev_state_change_handler+0x67e/0x9d0 [mlx5_core]
    blocking_notifier_call_chain+0xd5/0x130
    mlx5_vhca_state_work_handler+0x2b0/0x3f0 [mlx5_core]
    process_one_work+0x7c2/0x1340
    worker_thread+0x59d/0xec0
    kthread+0x28f/0x330
    ret_from_fork+0x1f/0x30

    other info that might help us debug this:

    Possible unsafe locking scenario:

    CPU0 CPU1
    ---- ----
    lock(&(&notifier->n_head)->rwsem);
    lock(&dev->intf_state_mutex);
    lock(&(&notifier->n_head)->rwsem);
    lock(&dev->intf_state_mutex);

    *** DEADLOCK ***

    4 locks held by kworker/u20:0/8:
    #0: ffff888150612938 ((wq_completion)mlx5_events){+.+.}-{0:0}, at: process_one_work+0x6e2/0x1340
    #1: ffff888100cafdb8 ((work_completion)(&work->work)#3){+.+.}-{0:0}, at: process_one_work+0x70f/0x1340
    #2: ffff888101aa7898 (&(&notifier->n_head)->rwsem){++++}-{3:3}, at: blocking_notifier_call_chain+0x5a/0x130
    #3: ffff88813682d0e8 (&dev->mutex){....}-{3:3}, at:__device_attach+0x76/0x460

    stack backtrace:
    CPU: 6 PID: 8 Comm: kworker/u20:0 Not tainted 5.19.0-rc8+
    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
    Workqueue: mlx5_events mlx5_vhca_state_work_handler [mlx5_core]
    Call Trace:
    <TASK>
    dump_stack_lvl+0x57/0x7d
    check_noncircular+0x278/0x300
    ? print_circular_bug+0x460/0x460
    ? lock_chain_count+0x20/0x20
    ? register_lock_class+0x1880/0x1880
    __lock_acquire+0x2fc7/0x6720
    ? register_lock_class+0x1880/0x1880
    ? register_lock_class+0x1880/0x1880
    lock_acquire+0x1c1/0x550
    ? mlx5_init_one+0x2e/0x490 [mlx5_core]
    ? lockdep_hardirqs_on_prepare+0x400/0x400
    __mutex_lock+0x12c/0x14b0
    ? mlx5_init_one+0x2e/0x490 [mlx5_core]
    ? mlx5_init_one+0x2e/0x490 [mlx5_core]
    ? _raw_read_unlock+0x1f/0x30
    ? mutex_lock_io_nested+0x1320/0x1320
    ? __ioremap_caller.constprop.0+0x306/0x490
    ? mlx5_sf_dev_probe+0x269/0x370 [mlx5_core]
    ? iounmap+0x160/0x160
    mlx5_init_one+0x2e/0x490 [mlx5_core]
    mlx5_sf_dev_probe+0x29c/0x370 [mlx5_core]
    ? mlx5_sf_dev_remove+0x130/0x130 [mlx5_core]
    auxiliary_bus_probe+0x9d/0xe0
    really_probe+0x1e0/0xaa0
    __driver_probe_device+0x219/0x480
    ? auxiliary_match_id+0xe9/0x140
    driver_probe_device+0x49/0x130
    __device_attach_driver+0x1b8/0x280
    ? driver_allows_async_probing+0x140/0x140
    bus_for_each_drv+0x123/0x1a0
    ? bus_for_each_dev+0x1a0/0x1a0
    ? lockdep_hardirqs_on_prepare+0x286/0x400
    ? trace_hardirqs_on+0x2d/0x100
    __device_attach+0x1a3/0x460
    ? device_driver_attach+0x1e0/0x1e0
    ? kobject_uevent_env+0x22d/0xf10
    bus_probe_device+0x1a2/0x260
    device_add+0x9b1/0x1b40
    ? dev_set_name+0xab/0xe0
    ? __fw_devlink_link_to_suppliers+0x260/0x260
    ? memset+0x20/0x40
    ? lockdep_init_map_type+0x21a/0x7d0
    __auxiliary_device_add+0x88/0xc0
    ? auxiliary_device_init+0x86/0xa0
    mlx5_sf_dev_state_change_handler+0x67e/0x9d0 [mlx5_core]
    blocking_notifier_call_chain+0xd5/0x130
    mlx5_vhca_state_work_handler+0x2b0/0x3f0 [mlx5_core]
    ? mlx5_vhca_event_arm+0x100/0x100 [mlx5_core]
    ? lock_downgrade+0x6e0/0x6e0
    ? lockdep_hardirqs_on_prepare+0x286/0x400
    process_one_work+0x7c2/0x1340
    ? lockdep_hardirqs_on_prepare+0x400/0x400
    ? pwq_dec_nr_in_flight+0x230/0x230
    ? rwlock_bug.part.0+0x90/0x90
    worker_thread+0x59d/0xec0
    ? process_one_work+0x1340/0x1340
    kthread+0x28f/0x330
    ? kthread_complete_and_exit+0x20/0x20
    ret_from_fork+0x1f/0x30
    </TASK>

    Fixes: 6a3273217469 ("net/mlx5: SF, Port function state change support")
    Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
    Reviewed-by: Shay Drory <shayd@nvidia.com>
    Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/ethernet/mellanox/mlx5/core/main.c | 4 ++++
    include/linux/mlx5/driver.h | 1 +
    2 files changed, 5 insertions(+)

    diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c b/drivers/net/ethernet/mellanox/mlx5/core/main.c
    index ba2e5232b90be..616207c3b187a 100644
    --- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
    +++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
    @@ -1472,7 +1472,9 @@ int mlx5_mdev_init(struct mlx5_core_dev *dev, int profile_idx)
    memcpy(&dev->profile, &profile[profile_idx], sizeof(dev->profile));
    INIT_LIST_HEAD(&priv->ctx_list);
    spin_lock_init(&priv->ctx_lock);
    + lockdep_register_key(&dev->lock_key);
    mutex_init(&dev->intf_state_mutex);
    + lockdep_set_class(&dev->intf_state_mutex, &dev->lock_key);

    mutex_init(&priv->bfregs.reg_head.lock);
    mutex_init(&priv->bfregs.wc_head.lock);
    @@ -1527,6 +1529,7 @@ int mlx5_mdev_init(struct mlx5_core_dev *dev, int profile_idx)
    mutex_destroy(&priv->bfregs.wc_head.lock);
    mutex_destroy(&priv->bfregs.reg_head.lock);
    mutex_destroy(&dev->intf_state_mutex);
    + lockdep_unregister_key(&dev->lock_key);
    return err;
    }

    @@ -1545,6 +1548,7 @@ void mlx5_mdev_uninit(struct mlx5_core_dev *dev)
    mutex_destroy(&priv->bfregs.wc_head.lock);
    mutex_destroy(&priv->bfregs.reg_head.lock);
    mutex_destroy(&dev->intf_state_mutex);
    + lockdep_unregister_key(&dev->lock_key);
    }

    static int probe_one(struct pci_dev *pdev, const struct pci_device_id *id)
    diff --git a/include/linux/mlx5/driver.h b/include/linux/mlx5/driver.h
    index 5040cd774c5a3..b0b4ac92354a2 100644
    --- a/include/linux/mlx5/driver.h
    +++ b/include/linux/mlx5/driver.h
    @@ -773,6 +773,7 @@ struct mlx5_core_dev {
    enum mlx5_device_state state;
    /* sync interface state */
    struct mutex intf_state_mutex;
    + struct lock_class_key lock_key;
    unsigned long intf_state;
    struct mlx5_priv priv;
    struct mlx5_profile profile;
    --
    2.35.1


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