Commits
Jason Gunthorpe committed 621e55ff5b8
RDMA/devices: Do not deadlock during client removal
lockdep reports:
WARNING: possible circular locking dependency detected
modprobe/302 is trying to acquire lock:
0000000007c8919c ((wq_completion)ib_cm){+.+.}, at: flush_workqueue+0xdf/0x990
but task is already holding lock:
000000002d3d2ca9 (&device->client_data_rwsem){++++}, at: remove_client_context+0x79/0xd0 [ib_core]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&device->client_data_rwsem){++++}:
down_read+0x3f/0x160
ib_get_net_dev_by_params+0xd5/0x200 [ib_core]
cma_ib_req_handler+0x5f6/0x2090 [rdma_cm]
cm_process_work+0x29/0x110 [ib_cm]
cm_req_handler+0x10f5/0x1c00 [ib_cm]
cm_work_handler+0x54c/0x311d [ib_cm]
process_one_work+0x4aa/0xa30
worker_thread+0x62/0x5b0
kthread+0x1ca/0x1f0
ret_from_fork+0x24/0x30
-> #1 ((work_completion)(&(&work->work)->work)){+.+.}:
process_one_work+0x45f/0xa30
worker_thread+0x62/0x5b0
kthread+0x1ca/0x1f0
ret_from_fork+0x24/0x30
-> #0 ((wq_completion)ib_cm){+.+.}:
lock_acquire+0xc8/0x1d0
flush_workqueue+0x102/0x990
cm_remove_one+0x30e/0x3c0 [ib_cm]
remove_client_context+0x94/0xd0 [ib_core]
disable_device+0x10a/0x1f0 [ib_core]
__ib_unregister_device+0x5a/0xe0 [ib_core]
ib_unregister_device+0x21/0x30 [ib_core]
mlx5_ib_stage_ib_reg_cleanup+0x9/0x10 [mlx5_ib]
__mlx5_ib_remove+0x3d/0x70 [mlx5_ib]
mlx5_ib_remove+0x12e/0x140 [mlx5_ib]
mlx5_remove_device+0x144/0x150 [mlx5_core]
mlx5_unregister_interface+0x3f/0xf0 [mlx5_core]
mlx5_ib_cleanup+0x10/0x3a [mlx5_ib]
__x64_sys_delete_module+0x227/0x350
do_syscall_64+0xc3/0x6a4
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Which is due to the read side of the client_data_rwsem being obtained
recursively through a work queue flush during cm client removal.
The lock is being held across the remove in remove_client_context() so
that the function is a fence, once it returns the client is removed. This
is required so that the two callers do not proceed with destruction until
the client completes removal.
Instead of using client_data_rwsem use the existing device unregistration
refcount and add a similar client unregistration (client->uses) refcount.
This will fence the two unregistration paths without holding any locks.
Cc: <stable@vger.kernel.org>
Fixes: 921eab1143aa ("RDMA/devices: Re-organize device.c locking")
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Link: https://lore.kernel.org/r/20190731081841.32345-2-leon@kernel.org
Signed-off-by: Doug Ledford <dledford@redhat.com>