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bh=MgLBSHEh8UXx8Lwl0jotaSYPe2tp0FAANULSTsLkn3Q=; b=AbOvEgbLYTnzXztzVAJoGre9X7JkZrE8MfnDKf+2NMu76vlbazen2ylTiENXGAl0PKNHkL j15LF8wDG5Hg7JQznD16Sry3NUI89CqhFO3P3ytfi8tyPX6vbo7B0MErcKOqXFac1d54oI B2d3NbkVZZEmSebf/QfyL0HPsDNyajk= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=NuBfxsmj; spf=pass (imf18.hostedemail.com: domain of sj@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 99D636111A; Mon, 23 Mar 2026 15:16:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 324B7C2BCB1; Mon, 23 Mar 2026 15:16:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774278974; bh=rdbRhrKbHgPbTB2eBO7rPqqHzWm6kls466VYWyJawKw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NuBfxsmjLxbFgFWYVtf/btgoy7qNqLJvpYKEUxhbxEREXuWedtGIOvofsBVEtuuAE p1WGwzHpb6B1c0wjTr2tegrC0uJ7OF7JLXuLTQeo5YAHbCpUmRpuZJm+JhMBMV3ymQ mErs2aF9RDwVEeAevgSwC+IDsUcM4frXP9tUYbcz+ZxgI4kpztC94TIEvaNoKoaM0h SwpUX8J7m/XFs8FspLbulnkAorpu6iMxX1rfm5XftzB48jcyIb3UNjRmoB0uB52UMC 3/k78opIpuZZSrKHp+kNtSlj6fEhg0xwqalyYTz6oS6JK42BP+KIy0AJrSg34j42Rp E59DZqMhjRrlg== From: SeongJae Park To: Liew Rui Yan Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: [RFC v4] mm/damon: add synchronous commit for commit_inputs Date: Mon, 23 Mar 2026 08:16:10 -0700 Message-ID: <20260323151611.81358-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260323141955.20535-1-aethernet65535@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 3D8601C001B X-Stat-Signature: tiwu1i18cj5xw3xmot3si4jioi6jnbnd X-HE-Tag: 1774278975-928196 X-HE-Meta: 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 ty1XkZI6 e7uGZX+epfAG/77ybjmgCA9gqzp1mbF0/MedFRsXtlrZnQDxUVFrtgdxX33UTCr5nqkXWIvFK11AQvHqxcIMyVH13qs+TNC/g0dFiKz82LNBW+xy76MksHr0I9Ptn3wdYFMWwqIm9CkoZnJOl3QwYyz1yWPe0h8Mz8I5wrA1tXmdHAYCk7DmRJll4HQ9CvN+aE/kiKnuVRa17ZYZrziwAwYDuiWQbM9yUayYa+flmTmEGbu5DFCGj513b9Qdg7qPABlgpYk+qXTBjE76IB4+m8cg0Cg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 23 Mar 2026 22:19:55 +0800 Liew Rui Yan wrote: > Hi SeongJae, > > Follow-up on my previous email regarding the locking concerns. > > > I admit I don't have an elegant solution yet. Here are my current > > thought: > > > > Add a timeout to wait_for_completion() (e.g., > > wait_for_completion_timeout()), using 'damos_watermarks.interval' as the > > upper bound. This prevents indefinite blocking of 'param_lock', though > > it still holds the global lock for up to several seconds. > > After further analysis, I realized that since both 'commit_inputs' and > 'enabled' module parameters are protected by the global 'param_lock', > stopping kdamond gracefully (via enabled=N) is serialized with > 'commit_inputs' writes. Therefore, a classic deadlock scenario should > not occur in normal operation. > > However, I'm considering edge cases where kdamond might terminate > unexpectedly. In such cases, commit_inputs_store() could hold > 'param_lock' indefinitely, blocking other module parameter updates > system-wide. > > To mitigate this risk defensively, would you accept adding a timeout to > wait_for_completion()? This ensures 'param_lock' is eventually released > even if kdamond fails unexpectedly. > > Please let me know your preference. :> As I mentioned on the reply to the original mail of this mail, I think such infinite wait will not happen because damon_call() is aware of the kdamond stop, and therefore the timeout is not needed. Please double check and let me know if I'm missing something, though, as a reply to my reply. Thanks, SJ [...]