From nobody Thu Apr 9 23:25:12 2026 Received: from mail-pj1-f53.google.com (mail-pj1-f53.google.com [209.85.216.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5FA77800 for ; Thu, 5 Mar 2026 06:19:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.53 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772691544; cv=none; b=U3oaT0AfupSa2RC+Ywr9ZAFK+pqcqn1nQWKBPoxqOa0L46K2UBV+58z21EFlZPiPpU49OMMfzEvTQmoTwKqsl4TMIcSVOr+Q0OeJO3SDI7E2UfLgqkHdXb+ac8N2V1X+sbkkBm3SH7b5nLomgnfqWmzICffwZ5lEB1ThFb+cyYY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772691544; c=relaxed/simple; bh=1ydMNjvWWWNJ8MmZbnh9xxYkl1ttV69Z8xgx9T/SRww=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=d3PFAEHV4hFfXkk1aY2CPOUi2qkK1cOO6rU33UMAiuDNYqIViLqBWB5NXaeWZwIfbICD2LwaqxTaOCwYigkkzl/uBL1he/j80yDRP8KHEgeCPq64yEMFwqbHcPMU9OvFD7xIeBV84qAF9GqDUipiu+Ij5l2uyzWQ1mXfC+dxDfM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=mPm6p/tl; arc=none smtp.client-ip=209.85.216.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="mPm6p/tl" Received: by mail-pj1-f53.google.com with SMTP id 98e67ed59e1d1-3598b2318c2so2486236a91.3 for ; Wed, 04 Mar 2026 22:19:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1772691543; x=1773296343; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=84DLa/5oWrs/xRCG5zCff7/tNADEE4rSWCOZvtWEwC8=; b=mPm6p/tlGFCxANSaZD5TrOzuM/uDRBJ+ArQVWAvk7pw7nis8TRaLJEzYwNhalEGbro EpLqclnAUiGzupbzcWnltH8BRd7MWT41HkWkPQROl5cpmVY0GaIKTVEfIDLWm0SLhfJn VkCtoUnIL5ov+fD2zpEO5Qx4eX6xATRaIz0LbqSotrhnAglg5CSXB1BRgM3T+6FJr22k tx1uqyAUdh1NSsvttsW5xNmnmZl9ddEVxfsKqnl2XEVI80NyqCfLHZZEIUIQ6h6eQDGW PeKPcSPzJ9kbPtIFcxu2kfN9kyp/jrlv6+Dw9jaVDOPbhp2WBwz2m+IJ7KL4TiXf9lK/ vKoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1772691543; x=1773296343; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=84DLa/5oWrs/xRCG5zCff7/tNADEE4rSWCOZvtWEwC8=; b=IJQ/j+ARpXFpclGdGGGgYSNGUKtqmllvh9AVwmmvSFNl5ILKyDt5H660XW4bRBk8Zy aTlVSr9EmAR5Ji5OSisA1Gld0CmhjoSqhmgGfs4zaa8zbGNaasqGD4AstKMGGVnAqlN2 srGdZn/hNdWoQdFZF8PsIqOGl130nMnPWFSzq3ONZ9Flgm1NDBOVDQD/PhKk/TzkZVrp lLuHwgXOEl/hbPtuCd6SpihQ+dW/3fBvvLJPLH8WOSLfwUX7c/T6V3SPwIG0w3iIgJdC L5vopGaFnTedOr35HPkdGDI26pzpXEKVkVRAvxU6IvkKUz4gZiizmUipELFgtj+B716B eLWA== X-Gm-Message-State: AOJu0Yxkj0GG2vi6pyQ6y88U9R1LpoT1feMP+mZCzWFmYSR8K1qsiDW0 EK2jG2S8wR73IAmHW+gcFDeG+SMCl/5vdFV27XrN2lyVGKui6PTVDb+Lf/1jdcsz X-Gm-Gg: ATEYQzxtymG4Qflhpl/5nOzOfjh8YUULRF561XwCS5ACsbjd2EpN2Tw8+fVc3RsGqVv KPggL8zSosed5qQ9Hm4sf6K+7329iYsKQ8VS1I+Nwlhsi4Modk7jCXKxerhk4iFVpWXdHmcoq/J qrJrDyMlLenABKjXX8b6TukTv24CJtGhQ59Sd7KRq0TvqxLfMuCw5164sTEYzxrwIhWOp1KkbM0 q6wrNZKE8yeOcQQfqjq0ouAwjxwzSv/3oj2wc/oHUwM1KTeF6GXlAx+6ijVE2DYLmu5cWLalwhQ U0SgbTOoPVNk9WBi3B4SkIo+63876m8ydnJTjb+6/JKb3xQcWj3poIOLUgsliXrUQ+bv4kBqavT gSh072YUaWp8vOUW2I/suukDCC6FGPXDLY5Jx6SK6lDTNBzuw+GeLQZtH9u0Ex0tGcDZoNtaQgi 0xnXDwu61uZ2+p9uHbPRKQBganKgJxlHG+n+E0+aJf8N6ZFu2WMMJQsMKfxU6xi2ZLw5gEQ/t21 Ok= X-Received: by 2002:a17:90a:d605:b0:343:6108:1712 with SMTP id 98e67ed59e1d1-359a6a21479mr4257139a91.18.1772691542586; Wed, 04 Mar 2026 22:19:02 -0800 (PST) Received: from mi-HP-ProDesk-680-G6-PCI-Microtower-PC.mioffice.cn ([43.224.245.226]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-359aa21e862sm1438145a91.4.2026.03.04.22.18.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Mar 2026 22:19:02 -0800 (PST) From: zhidao su X-Google-Original-From: zhidao su To: sched-ext@lists.linux.dev Cc: linux-kernel@vger.kernel.org, tj@kernel.org, void@manifault.com, arighi@nvidia.com, changwoo@igalia.com, peterz@infradead.org, mingo@redhat.com, zhidao su Subject: [PATCH] sched_ext: Use READ_ONCE() for lock-free reads of module param variables Date: Thu, 5 Mar 2026 14:18:56 +0800 Message-ID: <20260305061856.1796545-1-suzhidao@xiaomi.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" bypass_lb_cpu() reads scx_bypass_lb_intv_us and scx_slice_bypass_us without holding any lock, in timer callback context where module parameter writes via sysfs can happen concurrently: min_delta_us =3D scx_bypass_lb_intv_us / SCX_BYPASS_LB_MIN_DELTA_DIV; ^^^^^^^^^^^^^^^^^^^^ plain read -- KCSAN data race if (delta < DIV_ROUND_UP(min_delta_us, scx_slice_bypass_us)) ^^^^^^^^^^^^^^^^^ plain read -- KCSAN data race scx_bypass_lb_intv_us already uses READ_ONCE() in scx_bypass_lb_timerfn() and scx_bypass() for its other lock-free read sites, leaving bypass_lb_cpu() inconsistent. scx_slice_bypass_us has the same lock-free access pattern in the same function. Fix both plain reads by using READ_ONCE() to complete the concurrent access annotation and make the code KCSAN-clean. Signed-off-by: zhidao su --- kernel/sched/ext.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 1c3170846c84..9a1471ad5ae7 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4004,8 +4004,8 @@ static u32 bypass_lb_cpu(struct scx_sched *sch, struc= t rq *rq, * consider offloading iff the total queued duration is over the * threshold. */ - min_delta_us =3D scx_bypass_lb_intv_us / SCX_BYPASS_LB_MIN_DELTA_DIV; - if (delta < DIV_ROUND_UP(min_delta_us, scx_slice_bypass_us)) + min_delta_us =3D READ_ONCE(scx_bypass_lb_intv_us) / SCX_BYPASS_LB_MIN_DEL= TA_DIV; + if (delta < DIV_ROUND_UP(min_delta_us, READ_ONCE(scx_slice_bypass_us))) return 0; =20 raw_spin_rq_lock_irq(rq); --=20 2.43.0