From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794323898; b=4SIQLEAOwfawzSB70obDxIsPYBZYrMbQJSO/qwxqnbpllsHXk9NwTpoCoycSA7Jwx+Zl RTShHW/fIlECKP7AdeP96pAOnBN8FCzNXb891JcxqXhfyTD1wfFWgpNDB0MWi1Wp8wnZT OJMNB8VrYKZJF3Jhj3MkTaW6F+ETT4Zs5itcJ6vsdnf1ElOqzmVXwa0gTQgofDntSOlse vmncAfFSF+nQhkAPJq23ss+f8kQEpGYOwJ1I8UEHSlqI4URlvymxgXmP2xYVmtuZ5mz7a LIGP4iugXXOnMuDdofWVFhuNPe3LFU1+AtiIcBEKes1w3oys/wEkwatsrx366Iz7oaw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794323898; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=1l6xnI3pplMQ5fNPtII3/PwGcPbjMSVmoWDR9mkWvOo=; b=B4XKI3wyTMxNT8Cc2IHZWtVoQuFy0Fsx+D5tGQ9hRFmkj9l/LiK70vhLLovzK1QgvaEb URYcLkGKaJletgTvfhXVtzLmzi7AKv0zNUjM4k0+WQsdzVvRvDqBYUI9G2qB7efsc7AWa YNNpwa/rr5uAPjGYNQQr2w6DWFD3/fAtEu3syTJxIVTdvQXk3aC3x0ypaaz7pidqM9z5T bD99rp7jct7Q2GE0ikctixWEn2AkH5wROJWYnIYT7FXZFr94eY2qu9EDuzTtOGXpWUME9 3C4ZXTKayaa7AURQN9MLjiM+KUF5Sg3q9nMuKxvyVYOXkXQ1rirMS4ifNv3gjqX7eEg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=j05Aayfp; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BB5F6606A323 for ; Tue, 10 Nov 2026 15:18:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=j05Aayfp Received: by smtp.kernel.org (Postfix) with ESMTPSA id 35D3F1F0089F; Tue, 10 Nov 2026 15:18:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794323897; bh=1l6xnI3pplMQ5fNPtII3/PwGcPbjMSVmoWDR9mkWvOo=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=j05Aayfp9oaf71chPQc93cxzl2sVD+hf36HAJLbERUeN3UmJ/yMhHiKw9uA7OikXn kfiupV6L53KKfR8V4mJfVhQALaAD1O3h4/bX7wcduJvAdghQVREedNNaTHfztHbpNq vhwKUP1H6LjAv01HtXZ9o0273IZBwXfOO6vKxuinw8Tgj0nXk3XZT3GFIk4+cFhtCH ECIedI8QW+0QYKEZoxD2eGGoIGktQLhYpRdcUP3wqbTDgaq6ISzEbcnV3fo9H2fQwM 9PWeN0SoMo50Wfn371fwSYB9fkmBGM6XU1LKbjsJzeI36gfgW2SW1M/yHVgT0QWZ58 gnVsx+WjfWOVg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH 6.1.y] mm/damon/core: move static variable last_nr_regions to damon_ctx Reply-To: sashiko-reviews@lists.linux.dev To: "SJ Park" Cc: damon@lists.linux.dev In-Reply-To: <20261110151439.154208-1-sj@kernel.org> References: <20261109201705-failed-6.1-26ae50a0901a@kernel.org> <20261110151439.154208-1-sj@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 10 Nov 2026 15:18:16 +0000 X-Mailing-List: damon@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > kdamond_split_regions() uses a static variable last_nr_regions, to infer > if the region boundaries are too stable. If it looks too stable, it > does a more aggressive region split because it might be a fake stability > coming from non-aggressive split. Because the variable is static, the > inference can be racy and wrong when multiple kdamonds are running in > parallel. >=20 > The user impact is not critical. No crash, no leak. DAMON's > best-effort monitoring accuracy can be degraded when multiple kdamonds > are used in parallel and the workload has certain access patterns. Still > it is a bug that is better to fix. >=20 > Move the variable into the damon_ctx struct to fix the problem. >=20 > Link: https://lore.kernel.org/20261025164808.152048-3-sj@kernel.org > Fixes: 75c1c2b53c78 ("mm/damon/dbgfs: support multiple contexts") > Signed-off-by: SJ Park > Signed-off-by: Andrew Morton > Closes: https://sashiko.dev/#/bug/linux-eebfcdde-2881-48ef-8df1-e2019d2a4= 7f2 > Cc: Fernand Sieber > Cc: SeongJae Park > Cc: # 5.15.x > (cherry picked from commit 26ae50a0901a44f7d50053f87dc38abd9f9a269c) > Signed-off-by: SJ Park Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261110151439.1542= 08-1-sj@kernel.org?part=3D1