Boot regression (was "Re: [PATCH] genhd: Do not hold event lock when scheduling workqueue elements")

On 02/08/2017 03:48 AM, Dexuan Cui wrote:

quoted

From: Jens Axboe [mailto:axboe@kernel.dk]
Sent: Wednesday, February 8, 2017 00:09
To: Dexuan Cui <decui@microsoft.com>; Bart Van Assche
[off-list ref]; hare@suse.com; hare@suse.de
Cc: hch@lst.de; linux-kernel@vger.kernel.org; linux-block@vger.kernel.org;
jth@kernel.org
Subject: Re: [PATCH] genhd: Do not hold event lock when scheduling workqueue
elements

On 02/06/2017 11:29 PM, Dexuan Cui wrote:

quoted

quoted

From: linux-block-owner@vger.kernel.org [mailto:linux-block-
owner@vger.kernel.org] On Behalf Of Dexuan Cui
with the linux-next kernel.

I can boot the guest with linux-next's next-20170130 without any issue,
but since next-20170131 I haven't succeeded in booting the guest.

With next-20170203 (mentioned in my mail last Friday), I got the same
calltrace as Hannes.

With today's linux-next (next-20170206), actually the calltrace changed to
the below.
[  122.023036]  ? remove_wait_queue+0x70/0x70
[  122.051383]  async_synchronize_full+0x17/0x20
[  122.076925]  do_init_module+0xc1/0x1f9
[  122.097530]  load_module+0x24bc/0x2980

I don't know why it hangs here, but this is the same calltrace in my
last-Friday mail, which contains 2 calltraces. It looks the other calltrace has
been resolved by some changes between next-20170203 and today.

Here the kernel is trying to load the Hyper-V storage driver (hv_storvsc), and
the driver's __init and .probe have finished successfully and then the kernel
hangs here.

I believe something is broken recently, because I don't have any issue before
Jan 31.

Can you try and bisect it?

Jens Axboe

I bisected it on the branch for-4.11/next of the linux-block repo and the log shows
the first bad commit is 
[e9c787e6] scsi: allocate scsi_cmnd structures as part of struct request

# git bisect log
git bisect start
# bad: [80c6b15732f0d8830032149cbcbc8d67e074b5e8] blk-mq-sched: (un)register elevator when (un)registering queue
git bisect bad 80c6b15732f0d8830032149cbcbc8d67e074b5e8
# good: [309bd96af9e26da3038661bf5cdad780eef49dd9] md: cleanup bio op / flags handling in raid1_write_request
git bisect good 309bd96af9e26da3038661bf5cdad780eef49dd9
# bad: [27410a8927fb89bd150de08d749a8ed7f67b7739] nbd: remove REQ_TYPE_DRV_PRIV leftovers
git bisect bad 27410a8927fb89bd150de08d749a8ed7f67b7739
# bad: [e9c787e65c0c36529745be47d490d998b4b6e589] scsi: allocate scsi_cmnd structures as part of struct request
git bisect bad e9c787e65c0c36529745be47d490d998b4b6e589
# good: [3278255741326b6d66d8ca7d1cb2c57633ee43d9] scsi_dh_rdac: switch to scsi_execute_req_flags()
git bisect good 3278255741326b6d66d8ca7d1cb2c57633ee43d9
# good: [0fbc3e0ff623f1012e7c2af96e781eeb26bcc0d7] scsi: remove gfp_flags member in scsi_host_cmd_pool
git bisect good 0fbc3e0ff623f1012e7c2af96e781eeb26bcc0d7
# good: [eeff68c5618c8d0920b14533c70b2df007bd94b4] scsi: remove scsi_cmd_dma_pool
git bisect good eeff68c5618c8d0920b14533c70b2df007bd94b4
# good: [d48777a633d6fa7ccde0f0e6509f0c01fbfc5299] scsi: remove __scsi_alloc_queue
git bisect good d48777a633d6fa7ccde0f0e6509f0c01fbfc5299
# first bad commit: [e9c787e65c0c36529745be47d490d998b4b6e589] scsi: allocate scsi_cmnd structures as part of struct request

Christoph?

I've changed the subject line, this issue has nothing to do with the
issue that Hannes was attempting to fix.

-- 
Jens Axboe