From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f74.google.com (mail-wr1-f74.google.com [209.85.221.74]) (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 6036936A00E for ; Mon, 2 Feb 2026 13:59:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770040767; cv=none; b=jTk+3woNE+wfVwu+1DdgSxZX0zAxyMuJYxkU7BjJRCJWwOn5dzROT4eqmJuarHTlug7J7MbRgl9OsupJ8R0dZ9gqYAOhZR/2g253EsWMdRP12FGiKMT7IaaI4BKtDmy1LoKlUxdKJbj4mIlzIW85frg0PXh1ZWkViqfj6wp6pmc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770040767; c=relaxed/simple; bh=7GpqL5xBpxxOzYwK1ZiatJgtIrWZ25EwDTOzl8gLm3o=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=eBQbamC0zp3xkzfPHCUz9AfS3xM0MD51N6mwqGo8QN4+WTMd2PqOG7HOu6Iw106RSEBolTdK2h7YM1WEQmoO9ZlNVdTfzoC8x9gcK7UneLWmWatuy62b4IKBLq4g2/h5lKrUS86YR/QNeqj4uW+/h+Gwp+P0IVszZr7AQGcxgdo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jpiecuch.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=3W6y2UcX; arc=none smtp.client-ip=209.85.221.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jpiecuch.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="3W6y2UcX" Received: by mail-wr1-f74.google.com with SMTP id ffacd0b85a97d-4325b81081aso6386756f8f.3 for ; Mon, 02 Feb 2026 05:59:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1770040765; x=1770645565; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=45VMUXcTemBGf3CqcsoZ/vU9NbYkXPZ2OV0ZXsHP48U=; b=3W6y2UcX699iPw/r4/tm12c+EbAz0ho3UtF8aLfiZJyB27lPQdULMrEH9tlP8frjEW fusYWH7i1Sl8JlBe/s6nBcENOcNh+G6g4AFMzrPDJLtqcQQ4wH9/CB2Abx2gcb6t6FCf zyPNX49o6U9NN0gq3jgeGZF984wAcjZtPfG5wixsSEkQsVJGDG2oVFp7cuHtV6YuB4a7 1YprpTrIfsj03hftsYHJPMFxEVFS3MAEzG0K8aAVHqMa21e8P99SCz28mKToguxzSckg uGs/Wgiot8xforwOiybP1UWtZcZbCrJ7hEf2K63P8gh/lo0CkPivahVw/QWUzc46WuUn 9fvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1770040765; x=1770645565; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=45VMUXcTemBGf3CqcsoZ/vU9NbYkXPZ2OV0ZXsHP48U=; b=oyUMZC9Nef9PloS7+AaVWFK+VUscTSaQexkAWfjFA5ky4e+lfAcUR1WAe+Y7Z4rtZg 6ZmivIxksrYldQVkvvOEOcOE0YyBExfSF8XmpEG5zHEIqz9WTF43lHde4N2uU5PscvHU vy1LBuD+KBtnGBc6tfahVuDz3wrBxtU/AhDOI0D2oxocBWRBqQdARHex8oa4IWu6rPHx 4CfilCawFBt+iUCXh2bWqjvGga4ras8ABsiDR4Js/53A6nGDv2eiIUSjYLDbJ+iGsN6h AXsEyxqFNtXBTddCAsQsNROpfcdC4BqBhkHjZo/OidQJ5EcpxpFhYCxq5Ljls38eGoZH aXSQ== X-Forwarded-Encrypted: i=1; AJvYcCWE9zQt5h99LjsEN0eC60iEbedjs+PEPTTa3FwTPULA0e0JFu9uY2cx+sxUA5NZNSwTdY3+LYdSt6XPJNk=@vger.kernel.org X-Gm-Message-State: AOJu0YzGpvPDRFfmLc88J9BWYnoUgFDkK/JBxLVswgAuiqs9lJfGzl5a xhtNuMGjWwit2sVnIQpYmhMVvH19ar7jUkyAA4120PM1GiZvfw12w/flA0xjyJ45SM4nydAcYaa YJ8/6pArc7SlSlA== X-Received: from wrbch4.prod.google.com ([2002:a5d:5d04:0:b0:435:962c:27aa]) (user=jpiecuch job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:26c1:b0:430:f3ab:56af with SMTP id ffacd0b85a97d-435f3abc7b7mr16762977f8f.48.1770040764862; Mon, 02 Feb 2026 05:59:24 -0800 (PST) Date: Mon, 02 Feb 2026 13:59:24 +0000 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260201091318.178710-1-arighi@nvidia.com> <20260201091318.178710-2-arighi@nvidia.com> X-Mailer: aerc 0.21.0-0-g5549850facc2 Message-ID: Subject: Re: [PATCH 1/2] sched_ext: Fix ops.dequeue() semantics From: Kuba Piecuch To: Andrea Righi , Christian Loehle Cc: Tejun Heo , David Vernet , Changwoo Min , Kuba Piecuch , Emil Tsalapatis , Daniel Hodges , , Content-Type: text/plain; charset="UTF-8" Hi Andrea, On Mon Feb 2, 2026 at 7:45 AM UTC, Andrea Righi wrote: > diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c > index 6d6f1253039d8..d8fed4a49195d 100644 > --- a/kernel/sched/ext.c > +++ b/kernel/sched/ext.c > @@ -2248,7 +2248,7 @@ static void finish_dispatch(struct scx_sched *sch, struct rq *rq, > p->scx.flags |= SCX_TASK_OPS_ENQUEUED; > } else { > if (p->scx.flags & SCX_TASK_OPS_ENQUEUED) > - SCX_CALL_OP_TASK(sch, SCX_KF_REST, dequeue, task_rq(p), p, 0); > + SCX_CALL_OP_TASK(sch, SCX_KF_REST, dequeue, rq, p, 0); > > p->scx.flags &= ~SCX_TASK_OPS_ENQUEUED; > } This looks risky from a locking perspective. Are we relying on SCX_OPSS_DISPATCHING to protect against racing dequeues? If so, it might be worth calling out in a comment. Thanks, Kuba