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=1794321153; b=X/kZJ0gmVxOgMarIkOlFSShDjX6oJP8ZerUcVIvcJQHj2p13QaGkt73Exsw7/41WcNWI mAILv4rA3E97y6SED4lKK0LYodl+0yWRAjFt3Cm1eX0UyJKL+dU4+P5qDhNGnUi+t1exC DdIyciS2/mrYULaQhoUXpXMYWwjwTD10NK097gvPSgzdejadrbgj/X1GMbaDS+aNt3WGP BjYq84HLWhiWINLZ7RpLFj9POKY8rOg5+CoW+3BYAUa++rPnAvMfG0GZm6pPynMNdN2vh Ly5+ZQ8DqIvpcx+v0vOYA17jWBgIJoxysJR+jVVeCp+rbn2EOTSCba1OFlLZmHriO8A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794321153; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=LQoM5nOZNlBHX41/l/LlXZiZjsaHSH9kVooFnAbN0w8=; b=EZXmAOHoMG8t3oTGPWAi1KM/5WnSIU6FDBL3xqEFCzZkB4dRvcWDGIGQ7XmtZFDbl7+s QlPaThbUcMeB4gvWYQ7gyNcF90I0P+GWFFlrFfndxPqYxkLPw48dC5oH2tmMXxZcdGlmN +cyFG5BuC6GdmA6QkQX0IUVgtMMhY0axukPzmAHh54Dk6onZjvKunczmEEpMXFtHc4xAw tzyg2LW8rMKyQ8XqopHceJr/OP02aWYSXkt+vrTK5Pz7g5X4+pIdhW7EXDDSn1p5GNa86 WUu+AAi0VVafNmUqcKpx+SwgwtrvWi5wavHym6x6bf/GPNhpa+U6QtuinIBxtCylJQw== 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=kEuYXIlm; 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 B1BEA606A325 for ; Tue, 10 Nov 2026 14:32:32 +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=kEuYXIlm Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6FF931F0089F; Tue, 10 Nov 2026 14:32:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794321152; bh=LQoM5nOZNlBHX41/l/LlXZiZjsaHSH9kVooFnAbN0w8=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=kEuYXIlm6W8iZgkC8OJc1JrA2ZtlijRLmx8R/K+HOp3NseLu6KA0uto/5q+FZAVtO AilMLoilCO2tPfJ2s9dU2CUjLW102bpn2JMpotifm9GxowfLP5VRAnh9z2NgDbPjID 8DwVs5/wr4i231VdIjiFMpNdm1AvXTKIHYokAE6liGtyQH98SkpW5k0Mx+jfcEhwZ4 OqSvWIlWnzLg0T15KlOV1k3mHiUcM8pXwjVJ13Fg3z7/1FZFpkrW494dUXSZutvIpX O6JMdoz0udqjbgv8nUFjDwfx8d6qgQANHBY+NwV2SvrIpq1sw2PvJLqP5Wr8Rwxt92 etpY64WhuBoRQ== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH 6.18.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: <20261110142832.125968-1-sj@kernel.org> References: <20261109200407-failed-6.18-26ae50a0901a@kernel.org> <20261110142832.125968-1-sj@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 10 Nov 2026 14:32:31 +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/20261110142832.1259= 68-1-sj@kernel.org?part=3D1