From: Tejun Heo <tj@kernel.org>
To: Youfu Zhang <zhangyoufu@gmail.com>
Cc: axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: [BUG] blk-throttle panic on 32bit machine after startup
Date: Tue, 19 Oct 2021 07:45:57 -1000 [thread overview]
Message-ID: <YW8EVVmrQpuiwyEC@slm.duckdns.org> (raw)
In-Reply-To: <CAEKhA2x1Qi3Ywaj9fzdsaChabqDSMe2m2441wReg_V=39_Cuhg@mail.gmail.com>
On Mon, Oct 18, 2021 at 03:08:53PM +0800, Youfu Zhang wrote:
> Hi,
>
> I ran into a kernel bug related to blk-throttle on CentOS 7 AltArch for i386.
> Userspace programs may panic the kernel if they hit the I/O limit
> within 5 minutes after startup.
>
> Root cause:
> 1. jiffies was initialized to -300HZ during boot on 32bit machines
> 2. enable blkio cgroup hierarchy
> __DEVEL__sane_behavior for cgroup v1 or default hierarchy for cgroup v2
> EL7 kernel modified throtl_pd_init and always enable hierarchical throttling
> 3. enable & trigger blkio throttling within 5 minutes after startup
> bio propagated from child tg to parent
> 4. enter throtl_start_new_slice_with_credit
> if(time_after_eq(start, tg->slice_start[rw]))
> aka. time_after_eq(0xFFFxxxxx, 0) does not hold
> parent tg->slice_start[rw] was zero-initialized and not updated
> 5. enter throtl_trim_slice
> BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw]))
> aka. time_before(0xFFFxxxxx, 0) triggers a panic
This doesn't reproduce on 5.14.
Thanks.
--
tejun
next prev parent reply other threads:[~2021-10-19 17:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-18 7:08 [BUG] blk-throttle panic on 32bit machine after startup Youfu Zhang
2021-10-18 15:22 ` Liqueur Librazy
2021-10-19 17:45 ` Tejun Heo [this message]
2021-10-21 4:26 ` Youfu Zhang
-- strict thread matches above, loose matches on Subject: below --
2021-10-18 8:00 Haoran Luo
2021-10-18 9:25 Haoran Luo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YW8EVVmrQpuiwyEC@slm.duckdns.org \
--to=tj@kernel.org \
--cc=axboe@kernel.dk \
--cc=cgroups@vger.kernel.org \
--cc=linux-block@vger.kernel.org \
--cc=zhangyoufu@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox