linux-kernel - Re: [BUG REPORT] mm/damon: softlockup when kdamond walk page with cpu hotplug

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Message-Id: <20250930004907.55388-1-sj@kernel.org>
Date: Mon, 29 Sep 2025 17:49:07 -0700
From: SeongJae Park <sj@...nel.org>
To: Xinyu Zheng <zhengxinyu6@...wei.com>
Cc: SeongJae Park <sj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	damon@...ts.linux.dev,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	zouyipeng@...wei.com,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [BUG REPORT] mm/damon: softlockup when kdamond walk page with cpu hotplug

On Thu, 25 Sep 2025 19:11:13 +0800 Xinyu Zheng <zhengxinyu6@...wei.com> wrote:

> 
> 
> On 9/20/2025 6:42 PM, SeongJae Park wrote:
> > On Fri, 19 Sep 2025 20:56:56 -0700 (PDT) Hugh Dickins <hughd@...gle.com> wrote:
> > 
> >> On Thu, 18 Sep 2025, SeongJae Park wrote:
> >>
> >>> Hello,
> >>>
> >>> On Thu, 18 Sep 2025 03:00:29 +0000 Xinyu Zheng <zhengxinyu6@...wei.com> wrote:
> >>>
> >>>> A softlockup issue was found with stress test:
[...]
> > Xinyu, could you please test if the below attached patch fixes your issue and
> > let us know the result?
> > 
> > If Xinyu confirms the validity of the fix and no one objects to the above plan,
> > I will post the fix as a formal one with a better commit message.
> > 
> 
> Hi, SJ. The below attached patch is works!
> 
> These days, I reproduced the same softlockup scenario for three times. 
> It can be reproduced around an hour when I increase the memory pressure.
> Then I patched the below fix, and ran the same testcase whole day, 
> softlock didn't trigger again.
> 
> Sorry for the long wait. Thanks again for your solution and explanation!

Sorry for late response, and thank you for confirming that the fix works.  I
just posted it as a formal patch:
https://lore.kernel.org/20250930004410.55228-1-sj@kernel.org


Thanks,
SJ

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