linux-kernel - Re: Bug#1093243: Upgrade to 6.1.123 kernel causes mariadb hangs

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Message-ID: <Z5MkJ5sV-PK1m6_H@eldamar.lan>
Date: Fri, 24 Jan 2025 06:24:55 +0100
From: Salvatore Bonaccorso <carnil@...ian.org>
To: Pavel Begunkov <asml.silence@...il.com>
Cc: Xan Charbonnet <xan@...rbonnet.com>, 1093243@...s.debian.org,
	Jens Axboe <axboe@...nel.dk>, Bernhard Schmidt <berni@...ian.org>,
	io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Bug#1093243: Upgrade to 6.1.123 kernel causes mariadb hangs

HI Pavel, hi Jens,

On Thu, Jan 23, 2025 at 11:20:40PM +0000, Pavel Begunkov wrote:
> On 1/23/25 20:49, Salvatore Bonaccorso wrote:
> > Hi Xan,
> > 
> > On Thu, Jan 23, 2025 at 02:31:34PM -0600, Xan Charbonnet wrote:
> > > I rented a Linode and have been trying to load it down with sysbench
> > > activity while doing a mariabackup and a mysqldump, also while spinning up
> > > the CPU with zstd benchmarks.  So far I've had no luck triggering the fault.
> > > 
> > > I've also been doing some kernel compilation.  I followed this guide:
> > > https://www.dwarmstrong.org/kernel/
> > > (except that I used make -j24 to build in parallel and used make
> > > localmodconfig to compile only the modules I need)
> > > 
> > > I've built the following kernels:
> > > 6.1.123 (equivalent to linux-image-6.1.0-29-amd64)
> > > 6.1.122
> > > 6.1.121
> > > 6.1.120
> > > 
> > > So far they have all exhibited the behavior.  Next up is 6.1.119 which is
> > > equivalent to linux-image-6.1.0-28-amd64.  My expectation is that the fault
> > > will not appear for this kernel.
> > > 
> > > It looks like the issue is here somewhere:
> > > https://www.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.1.120
> > > 
> > > I have to work on some other things, and it'll take a while to prove the
> > > negative (that is, to know that the failure isn't happening).  I'll post
> > > back with the 6.1.119 results when I have them.
> > 
> > Additionally please try with 6.1.120 and revert this commit
> > 
> > 3ab9326f93ec ("io_uring: wake up optimisations")
> > 
> > (which landed in 6.1.120).
> > 
> > If that solves the problem maybe we miss some prequisites in the 6.1.y
> > series here?
> 
> I'm not sure why the commit was backported (need to look it up),
> but from a quick look it does seem to miss a barrier present in
> the original patch.

Ack, this was here for reference:
https://lore.kernel.org/stable/57b048be-31d4-4380-8296-56afc886299a@kernel.dk/

Xan Charbonnet was able to confirm in https://bugs.debian.org/1093243#99 that
indeed reverting the commit fixes the mariadb related hangs.

Regards,
Salvatore