linux-kernel - Re: [PATCH RFC -next] sbitmap: fix possible io hung due to lost wakeups

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Message-ID: <YqyJ7dwUB0z0puNc@kbusch-mbp.dhcp.thefacebook.com>
Date:   Fri, 17 Jun 2022 08:04:29 -0600
From:   Keith Busch <kbusch@...nel.org>
To:     Yu Kuai <yukuai3@...wei.com>
Cc:     axboe@...nel.dk, ming.lei@...hat.com, jack@...e.cz,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com
Subject: Re: [PATCH RFC -next] sbitmap: fix possible io hung due to lost
 wakeups

On Fri, Jun 17, 2022 at 10:11:25PM +0800, Yu Kuai wrote:
> 
> What's worse, io hung is possible in theory because wakeups might be
> missed. For example, 2 * wake_batch tags are put, while only wake_batch
> threads are worken:

Not just in theory, io hanging sounds like the problem reported here:

  https://bugzilla.kernel.org/show_bug.cgi?id=215679

I only knew that it had nothing to do with the nvme driver, though, but they
closed the bug after it stopped happening with different hardware.