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Message-ID: <YNqL+3LDsIPKm1ol@T590>
Date: Tue, 29 Jun 2021 10:56:59 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Wen Xiong <wenxiong@...ibm.com>
Cc: dwagner@...e.de, james.smart@...adcom.com,
linux-kernel@...r.kernel.org, sagi@...mberg.me
Subject: Re: [PATCH 1/1] block: System crashes when cpu hotplug + bouncing
port
Hi Wen Xiong,
On Tue, Jun 29, 2021 at 02:43:42AM +0000, Wen Xiong wrote:
> >>NVMe users have to pass correct hctx_idx to blk_mq_alloc_request_hctx(),
> but
> >>from the info you provided, they don't provide valid hctx_idx to blk-mq,
> so
> >>q->queue_hw_ctx[hctx_idx] is NULL and kernel panic.
>
> Hi Ming,
>
> Daniel's two patches didn't fix the crash issue. My patch is on top of two
> patches.
> That is the reason why I am continue debugging the issue.
Can you provide the dmesg log after applying Daniel's patches?
Yeah, one known issue is that the following line in blk_mq_alloc_request_hctx()
won't work well even though Daniel's patches are applied:
data.ctx = __blk_mq_get_ctx(q, cpu);
Is that the kernel crash in your observation?
>
> What hctx_idx you suggest to provide to blk-mq for this issue?
>
> Before cpu hotplug, num_online_cpus() is 16: 0-15 are online.
> After cpu hotplug, num_online_cpus() is 8: 0,1,2,3,8,9, 10,11 are online
> 4,5,6,7,12,13,14,15 are offline.
>
> What hctx_idx you suggest to provide to blk-mq by calling
> blk_mq_alloc_request_hctx() in this case?
At least the hctx_idx shouldn't be >= q->nr_hw_queues/set->nr_hw_queues.
Also can you collect the queue mapping log?
#./dump-qmap /dev/nvme1n1
[1] http://people.redhat.com/minlei/tests/tools/dump-qmap
Thanks,
Ming
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