From: Sagi Grimberg <sagi@grimberg.me>
To: kwb <wangbing.kuang@shopee.com>,
james.smart@broadcom.com, kbusch@kernel.org, axboe@fb.com,
hch@lst.de, linux-nvme@lists.infradead.org,
linux-kernel@vger.kernel.org
Cc: chunguang.xu@shopee.com
Subject: Re: [Bug Report] nvme connect deadlock in allocating tag
Date: Sun, 28 Apr 2024 11:10:43 +0300 [thread overview]
Message-ID: <d200fc7c-c781-49f1-8277-bdb5d537b1f4@grimberg.me> (raw)
In-Reply-To: <20240428063147.88058-1-wangbing.kuang@shopee.com>
On 28/04/2024 9:31, kwb wrote:
> Hi,
> We found nvme connect will dealock when it cannot alloc tag in admin queue. So we reproduce it and find a way to work around. The solution is to utilize reserve tag for connecting.
> Here is the deadlock environment:
> 1. the process [kworker/u129:1+nvme-wq] want to connect wait for geting tag, but tag is used up:
> [<0>] blk_mq_get_tag+0x11d/0x2d0
> [<0>] __blk_mq_alloc_request+0x92/0x180
> [<0>] blk_mq_alloc_request+0x7c/0xc0
> [<0>] nvme_alloc_request+0x28/0x100 [nvme_core]
> [<0>] __nvme_submit_sync_cmd+0x1ea/0x230 [nvme_core]
> [<0>] nvmf_reg_read64+0x62/0xa0 [nvme_fabrics]
> [<0>] nvme_enable_ctrl+0x25/0xb0 [nvme_core]
> [<0>] nvme_tcp_setup_ctrl+0x257/0x340 [nvme_tcp]
> [<0>] nvme_tcp_reconnect_ctrl_work+0x24/0x40 [nvme_tcp]
> [<0>] process_one_work+0x228/0x3d0
> [<0>] worker_thread+0x4d/0x3f0
> [<0>] kthread+0x127/0x150
> [<0>] ret_from_fork+0x1f/0x30
> 2. many processes (here is nvme list) is waiting for connecting:
> [<0>] blk_execute_rq+0x8d/0x110
> [<0>] nvme_execute_passthru_rq+0x60/0x1f0 [nvme_core]
> [<0>] nvme_submit_user_cmd+0x23e/0x400 [nvme_core]
> [<0>] nvme_user_cmd+0x163/0x1d0 [nvme_core]
> [<0>] nvme_ctrl_ioctl+0x2e/0x40 [nvme_core]
> [<0>] __nvme_ioctl+0x78/0xc0 [nvme_core]
> [<0>] nvme_ioctl+0x1e/0x20 [nvme_core]
> [<0>] blkdev_ioctl+0x126/0x260
> [<0>] block_ioctl+0x4a/0x60
> [<0>] __x64_sys_ioctl+0x91/0xc0
> [<0>] do_syscall_64+0x59/0xc0
> [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> Reproduce method is very eazy:
> 1. call many nvme list
> 2. make nvme io timeout to recover connection
> 3. trick is to make reconnect-delay much time, eg:30s
>
> The solution is the appending patch. it is tested and also consider keepalive and reset/showdown tag reserve.
The error_recovery work should unquiesce the admin_q, which should fail
fast all pending admin commands,
so it is unclear to me how the connect process gets stuck.
What is step (2) - make nvme io timeout to recover the connection?
Is this reproducing with upstream nvme? or is this some distro kernel
where this happens?
Do you have the below patch applied?
de105068fead ("nvme: fix reconnection fail due to reserved tag allocation")
next prev parent reply other threads:[~2024-04-28 8:10 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-28 6:31 [Bug Report] nvme connect deadlock in allocating tag kwb
2024-04-28 8:10 ` Sagi Grimberg [this message]
[not found] ` <CAG89T6Yyx4f6Dt__L=Ku4AwCzuEUhEOOEjuXbdE+GSSqVJVZ-g@mail.gmail.com>
2024-04-28 9:30 ` Sagi Grimberg
2024-04-28 10:25 ` kwb
2024-04-28 12:38 ` Sagi Grimberg
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