From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5E3DA2FFDDF; Thu, 18 Sep 2025 08:57:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758185824; cv=none; b=iegZE0l8NxM/VkobkaFNybCz05fZZTI3ElBhZGfQmR9h+a2GFCLXHWQgi5ynqWz/XH4lyN0LiGjZbbyTcK79cIAG2K59XGkrP6SwuuSm3wZWiZwB5M9yBYfMWBLw4P6BRYAgo2wRv7YoDMEmH2dx9XVHERImyY5zmQ94ImlrmEk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758185824; c=relaxed/simple; bh=yxVfx5vksXDs9huAM4+ZQ9ZyJNmrE6WNGXBbv/HqT44=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=G3hQ2cd9zVgxmvn9yesV6nIOlpHmwxlvi5vqCIBt2Now5T3lpyl/g3ES1S5/a9md/eP9cDQdIEx2c0pF8PpxHplt0KA5UfXuVYeEoYlQ1F8VnQ7WDqTRJ48xg2g404nIEhLFZo0WxrWtBr/NbuS6ukmZAO+yEbHI2RTRi/7pY5U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FIpu3YQa; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FIpu3YQa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C68A4C4CEE7; Thu, 18 Sep 2025 08:57:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758185824; bh=yxVfx5vksXDs9huAM4+ZQ9ZyJNmrE6WNGXBbv/HqT44=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FIpu3YQaEHDt818JLn/nm2GtOYrzyhdhz83htetfkYXX6SkNWnA27Ed6d7kfqctDl w8vd+J+NGkBYxCi6K5+2x7Gh7Bcoc7wWp7dH25eD+6B2jn3FjZgO7PDND3TotLoy4y 4MNePD7xijGTBV9FQWDU0l7IsSF86fJ7V+RC4Ux1FCY1Z/fFE2JsFZWYz5dDMB+g1N TPHf53GH4+yWYDOG7uKDawE9o2N1T+2GiungfCsM8LL4AP/f635yUz+QdiUWjTY5xg yBsXvKT3gJV06lsfFfS/J/I9njYtM04lmqEjq83f6/tphV9MkRWhfiIuX5PT5n0DZC Q0obo36sVHc4A== From: SeongJae Park To: SeongJae Park Cc: Xinyu Zheng , Andrew Morton , "Paul E . McKenney" , Peter Zijlstra , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, zouyipeng@huawei.com, Hugh Dickins Subject: Re: [BUG REPORT] mm/damon: softlockup when kdamond walk page with cpu hotplug Date: Thu, 18 Sep 2025 01:57:00 -0700 Message-Id: <20250918085701.59085-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250918085249.58966-1-sj@kernel.org> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Thu, 18 Sep 2025 01:52:49 -0700 SeongJae Park wrote: > Hello, > > On Thu, 18 Sep 2025 03:00:29 +0000 Xinyu Zheng 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 [...]