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

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Date:   Thu, 9 Feb 2017 14:08:00 +0100
From:   "hch@....de" <hch@....de>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Bart Van Assche <Bart.VanAssche@...disk.com>,
        "hare@...e.com" <hare@...e.com>, "hare@...e.de" <hare@...e.de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "jth@...nel.org" <jth@...nel.org>
Subject: Re: Boot regression (was "Re: [PATCH] genhd: Do not hold event
        lock when scheduling workqueue elements")

Hi Dexuan,

I've spent some time with the logs and looking over the code and
couldn't find any smoking gun.  I start to wonder if it might just
be a timing issue?

Can you try one or two things for me:

 1) run with the blk-mq I/O path for scsi by either enabling it a boot /
    module load time with the scsi_mod.use_blk_mq=Y option, or at compile
    time by enabling the CONFIG_SCSI_MQ_DEFAULT option.  If that fails
    with the commit a blk-mq run before the commit would also be useful.
 2) if possible run a VM config without the virtual CD-ROM drive -
    a lot of the scsi log chatter is about handling timeouts on the
    CD drive, so that might be able to isolate issues a bit better.

Note that I'll be offline from this afternoon European time until Sunday
night as I'm out in the mountains at a lodge without internet access,
but this issue will be my priority once back.