From mboxrd@z Thu Jan  1 00:00:00 1970
From: sagi@grimberg.me (Sagi Grimberg)
Date: Wed, 17 Aug 2016 21:57:34 +0300
Subject: nvmf/rdma host crash during heavy load and keep alive recovery
In-Reply-To: <045601d1f803$a9d73a20$fd85ae60$@opengridcomputing.com>
References: <018301d1e9e1$da3b2e40$8eb18ac0$@opengridcomputing.com>
 <20160801110658.GF16141@lst.de>
 <008801d1ec00$a0bcfbf0$e236f3d0$@opengridcomputing.com>
 <015801d1ec3d$0ca07ea0$25e17be0$@opengridcomputing.com>
 <010f01d1f31e$50c8cb40$f25a61c0$@opengridcomputing.com>
 <013701d1f320$57b185d0$07149170$@opengridcomputing.com>
 <018401d1f32b$792cfdb0$6b86f910$@opengridcomputing.com>
 <01a301d1f339$55ba8e70$012fab50$@opengridcomputing.com>
 <2fb1129c-424d-8b2d-7101-b9471e897dc8@grimberg.me>
 <004701d1f3d8$760660b0$62132210$@opengridcomputing.com>
 <008101d1f3de$557d2850$007778f0$@opengridcomputing.com>
 <00fe01d1f3e8$8992b330$9cb81990$@opengridcomputing.com>
 <01c301d1f702$d28c7270$77a55750$@opengridcomputing.com>
 <6ef9b0d1-ce84-4598-74db-7adeed313bb6@grimberg.me>
 <045601d1f803$a9d73a20$fd85ae60$@opengridcomputing.com>
Message-ID: <69c0e819-76d9-286b-c4fb-22f087f36ff1@grimberg.me>


>> If that is the case, I think we need to have a closer look at
>> nvme_stop_queues...
>>
>
> request_queue->queue_flags does have QUEUE_FLAG_STOPPED set:
>
> #define QUEUE_FLAG_STOPPED      2       /* queue is stopped */
>
> crash> request_queue.queue_flags -x 0xffff880397a13d28
>   queue_flags = 0x1f07a04
> crash> request_queue.mq_ops 0xffff880397a13d28
>   mq_ops = 0xffffffffa084b140 <nvme_rdma_mq_ops>
>
> So it appears the queue is stopped, yet a request is being processed for that
> queue.  Perhaps there is a race where QUEUE_FLAG_STOPPED is set after a request
> is scheduled?

Umm. When the keep-alive timeout triggers we stop the queues. only 10
seconds (or reconnect_delay) later we free the queues and reestablish
them, so I find it hard to believe that a request was queued, and spent
so long in queue_rq until we freed the queue-pair.

 From you description of the sequence it seems that after 10 seconds we
attempt a reconnect and during that time an IO request crashes the
party.

I assume this means you ran traffic during the sequence yes?