Re: [PATCH] RDMA/mlx5: Use irq xarray locking for mkey_table

[Leon Romanovsky <leonro@mellanox.com>]

On Fri, Oct 25, 2019 at 02:49:13AM +0300, Jason Gunthorpe wrote:
> The mkey_table xarray is touched by the reg_mr_callback() function which
> is called from a hard irq. Thus all other uses of xa_lock must use the
> _irq variants.
>
>   WARNING: inconsistent lock state
>   5.4.0-rc1 #12 Not tainted
>   --------------------------------
>   inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
>   python3/343 [HC0[0]:SC0[0]:HE1:SE1] takes:
>   ffff888182be1d40 (&(&xa->xa_lock)->rlock#3){?.-.}, at: xa_erase+0x12/0x30
>   {IN-HARDIRQ-W} state was registered at:
>     lock_acquire+0xe1/0x200
>     _raw_spin_lock_irqsave+0x35/0x50
>     reg_mr_callback+0x2dd/0x450 [mlx5_ib]
>     mlx5_cmd_exec_cb_handler+0x2c/0x70 [mlx5_core]
>     mlx5_cmd_comp_handler+0x355/0x840 [mlx5_core]
>    [..]
>
>    Possible unsafe locking scenario:
>
>          CPU0
>          ----
>     lock(&(&xa->xa_lock)->rlock#3);
>     <Interrupt>
>       lock(&(&xa->xa_lock)->rlock#3);
>
>    *** DEADLOCK ***
>
>   2 locks held by python3/343:
>    #0: ffff88818eb4bd38 (&uverbs_dev->disassociate_srcu){....}, at: ib_uverbs_ioctl+0xe5/0x1e0 [ib_uverbs]
>    #1: ffff888176c76d38 (&file->hw_destroy_rwsem){++++}, at: uobj_destroy+0x2d/0x90 [ib_uverbs]
>
>   stack backtrace:
>   CPU: 3 PID: 343 Comm: python3 Not tainted 5.4.0-rc1 #12
>   Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
>   Call Trace:
>    dump_stack+0x86/0xca
>    print_usage_bug.cold.50+0x2e5/0x355
>    mark_lock+0x871/0xb50
>    ? match_held_lock+0x20/0x250
>    ? check_usage_forwards+0x240/0x240
>    __lock_acquire+0x7de/0x23a0
>    ? __kasan_check_read+0x11/0x20
>    ? mark_lock+0xae/0xb50
>    ? mark_held_locks+0xb0/0xb0
>    ? find_held_lock+0xca/0xf0
>    lock_acquire+0xe1/0x200
>    ? xa_erase+0x12/0x30
>    _raw_spin_lock+0x2a/0x40
>    ? xa_erase+0x12/0x30
>    xa_erase+0x12/0x30
>    mlx5_ib_dealloc_mw+0x55/0xa0 [mlx5_ib]
>    uverbs_dealloc_mw+0x3c/0x70 [ib_uverbs]
>    uverbs_free_mw+0x1a/0x20 [ib_uverbs]
>    destroy_hw_idr_uobject+0x49/0xa0 [ib_uverbs]
>    [..]
>
> Fixes: 0417791536ae ("RDMA/mlx5: Add missing synchronize_srcu() for MW cases")
> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
> ---
>  drivers/infiniband/hw/mlx5/mr.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>

Thanks,
Acked-by: Leon Romanovsky <leonro@mellanox.com>