Re: [PATCH v2 for-next] IB/SA: Check dlid before SA agent queries for ClassPortInfo

[Jason Gunthorpe <jgg-uk2M96/98Pc@public.gmane.org>]

On Mon, Dec 18, 2017 at 07:26:58PM -0800, Dennis Dalessandro wrote:
> From: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> 
> SA queries SM for class port info when there is a LID_CHANGE event.
> 
> When a base lid is configured before fm is started ie when smlid is
> not yet assigned, SA handles the LID_CHANGE event and tries query SM
> with lid 0. This will cause an hang.
> 
> [ 1106.958820] INFO: task kworker/2:0:23 blocked for more than 120 seconds.
> [ 1106.965082] Tainted: G O 4.12.0+ #1
> [ 1106.969602] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
>  this message.
> [ 1106.977227] kworker/2:0 D 0 23 2 0x00000000
> [ 1106.977250] Workqueue: infiniband update_ib_cpi [ib_core]
> [ 1106.977261] Call Trace:
> [ 1106.977273] __schedule+0x28e/0x860
> [ 1106.977285] schedule+0x36/0x80
> [ 1106.977298] schedule_timeout+0x1a3/0x2e0
> [ 1106.977310] ? radix_tree_iter_tag_clear+0x1b/0x20
> [ 1106.977322] ? idr_alloc+0x64/0x90
> [ 1106.977334] wait_for_completion+0xe3/0x140
> [ 1106.977347] ? wake_up_q+0x80/0x80
> [ 1106.977369] update_ib_cpi+0x163/0x210 [ib_core]
> [ 1106.977381] process_one_work+0x147/0x370
> [ 1106.977394] worker_thread+0x4a/0x390
> [ 1106.977406] kthread+0x109/0x140
> [ 1106.977418] ? process_one_work+0x370/0x370
> [ 1106.977430] ? kthread_park+0x60/0x60
> [ 1106.977443] ret_from_fork+0x22/0x30
> 
> Always ensure a proper smlid is assigned before querying SM for cpi.

Shouldn't we do something about this long hang as well?

> Fixes: ee1c60b1bff ("IB/SA: Modify SA to implicitly cache Class Port info")
> Reviewed-by: Ira Weiny <ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Dennis Dalessandro <dennis.dalessandro-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Otherwise seems like a reasonable step to me..

Jason
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