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From: SeongJae Park <sj@kernel.org>
To: SeongJae Park <sj@kernel.org>
Cc: Xinyu Zheng <zhengxinyu6@huawei.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	damon@lists.linux.dev, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, zouyipeng@huawei.com,
	Hugh Dickins <hughd@google.com>
Subject: Re: [BUG REPORT] mm/damon: softlockup when kdamond walk page with cpu hotplug
Date: Thu, 18 Sep 2025 01:57:00 -0700	[thread overview]
Message-ID: <20250918085701.59085-1-sj@kernel.org> (raw)
In-Reply-To: <20250918085249.58966-1-sj@kernel.org>

On Thu, 18 Sep 2025 01:52:49 -0700 SeongJae Park <sj@kernel.org> wrote:

> Hello,
> 
> On Thu, 18 Sep 2025 03:00:29 +0000 Xinyu Zheng <zhengxinyu6@huawei.com> wrote:
> 
> > A softlockup issue was found with stress test:
[...]
> damon_mkold_pmd_entry() calls pte_offset_map_lock().  If the call returns an
> error, damon_mkold_pmd_entry() sets walk->action as ACTION_AGAIN, to retry.  If
> the pte_offset_map_lock() continues fails, infinite loop can happen.  I
> understand the loop you mentioned above is this case.
> 
> The error handling (retrying) was introduced by commit 7780d04046a2
> ("mm/pagewalkers: ACTION_AGAIN if pte_offset_map_lock() fails").

I added Hugh to this thread from the original mail of this reply, because he is
the author of the commit.  I should clarified this on the original mail but
forgot saying that, sorry.


Thanks,
SJ

[...]

  reply	other threads:[~2025-09-18  8:57 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-18  3:00 [BUG REPORT] mm/damon: softlockup when kdamond walk page with cpu hotplug Xinyu Zheng
2025-09-18  8:52 ` SeongJae Park
2025-09-18  8:57   ` SeongJae Park [this message]
2025-09-20  3:56   ` Hugh Dickins
2025-09-20 10:42     ` SeongJae Park
2025-09-22  3:48       ` Xinyu Zheng
2025-09-25 11:11       ` Xinyu Zheng
2025-09-30  0:49         ` SeongJae Park

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