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=1794323096; b=3sCAXYRLbHWFChk6lGsO4p5NQ+gvBrRsSBQN+rilttyn1t+Kj/ZTu3Q+Rbj+fXeMUrXW hG+vwt9WgLJjRK1VBtt4sbCuyQuHVC12hJ200OM/iQAYe9/mWiAjqAe13uChTRzc91lUE KqyLhtDpZa3jRK6VzWW9avAm4hYuoedVChY13+68AvkFkqRoW2G09xeQxOIN9PayuOAja cH15LWh0Sdr+Ard2p5bkenYecP9TqYnGn7Meo+EWzMS3eZkzI+T7pDrr7cC4ykc1Sgta3 fUfgt3IpG2+g1lIctWTQm4bdDiZra/nXbc6H9Jb4AJ+q82dJp0wW/j5TCrk4x7LzuNw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794323096; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=9dEweRwLlWQhzcLy7MeqaPr4Vy5b9M+n3HN4sPq35HA=; b=u4ys2eVuKhwWoSNytCniUt4WsRTTowRs+u/9Cx7YX7IppK91EWvqw2LeQhBTQOsWAjfx +lVyMW3uH6m9jFLFEnCg853n2RERbfpFtLNY1JumcR6c+PAAAcp/KRX+9dJmyZQs/qeIy phepXfWwkENJT/QLvPZWPdLk9aaAOV/LvCTejn1IDablf9vN4fYYQ6Z4rVEgcNBd6Vnzu nQ5N05/of+KJI7orPXep38IV+rkvvxKYO4JGjkhjzd1W++HnimhfdpYW6fCpP9/zbYg8c 6KaTy3fkNx66mHyLv6kviZq6gsObUPKddfA8/wfCvJ+eZbtMFG39I+62LxFDwkSWB0Q== 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=RV72nbmi; 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 C506960A2600 for ; Tue, 10 Nov 2026 15:04:55 +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=RV72nbmi Received: by smtp.kernel.org (Postfix) with ESMTPSA id 82F4B1F0093D; Tue, 10 Nov 2026 15:04:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794323095; bh=9dEweRwLlWQhzcLy7MeqaPr4Vy5b9M+n3HN4sPq35HA=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=RV72nbmiwFo20Qz3z+Q949L45wHtDC7e4PcGVikzEY9WvzdcmxfibfyDsuCwfXqeP Cw8UlNp/dP4ctO4f6wySC5XKaIp3/3o/UB1BH85tnlVzpEi/yATzgCTvBm9yvDNBjB B3W5rDayxNzL2KoYDkQTs6kxfhc8rIcrpmcA/zvVEHwSbIkQy+KzgTmxayusUPR2Wv XBuQ8Gqc7EckMdT9MyOU3WhGFajOUBgUw80+Cu83JyAbL8l29Nj/nTIy7BvHxi6NUj M9mGTcEc4zvH4rub2Z1NkFKEA5uri08Whx7dWCxguQT+gdvzntYfUohjNvxHg8cP2Y AEOqLySHibUtA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH 6.12.y v2] 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: <20261110150218.145605-1-sj@kernel.org> References: <20261109200803-failed-6.12-26ae50a0901a@kernel.org> <20261110150218.145605-1-sj@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 10 Nov 2026 15:04:55 +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/20261110150218.1456= 05-1-sj@kernel.org?part=3D1