From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7B12113D265 for ; Wed, 17 Apr 2024 13:14:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713359650; cv=none; b=B7ZyUHs678MTVACXIbC6TqNgYzNCNWtFIwlZKj0Aawi8PVldDK1wRXj1zsp6EO4dE9Qhokmz0DBzO8Yud4ulhNy/MZIu6xiqevQpyfyVndmB90L364Gqz7SqlS1neICeB8/rSuwJ+Wkcf8Ql66OS3tSyTI6z/2I7MO2GSHyyaAg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713359650; c=relaxed/simple; bh=jwJJ8rkbGnXillPq8GD+1sFN4L9SJymklLL4WgTsdsg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=MyzXJV/SA2fDTx2WmRJA+Zzi5Rxw4FVH9cBZOCw1NzW7LyhVSCX1ZArwCpgn2WNPPe4ZSpda55720pQqAD2QpwompMtC1zOamjrEAOfE3uuvXDZ6Nk3w1lXJxo81DcnP/cpDs/AWRnBWxT2n6EdyWHLdxlSSgpJpWcy5IES8N1g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RgGKogq/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RgGKogq/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D700C3277B; Wed, 17 Apr 2024 13:14:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713359649; bh=jwJJ8rkbGnXillPq8GD+1sFN4L9SJymklLL4WgTsdsg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RgGKogq/TQniHcx8btt6qatA2o8ABb/MHVZFOUj+07+kZ8jU+Xc2KgTzyYJQwgiDO nVIf46qTd2XPtYXfeH/MQyFjd+RhFQRqC4BLzpyZmOLM9w8f4k+28wO17MnFDyLyO3 GvppJCH2PfibKacMa4NE1mvhk14JEis2RvYe9vrNWmwlw09vfWzvA6HG4cxbWSZBOO 0B7NrZq360tefPsUDO4f/e+NQx1syeNupFGpjsBzZVRnwUsKpR3kyqaynhlrZicSV6 Q+ScKqP4qTLlE+hXEg5xkCIEtomMfRyEj8H0rpz1Y425d04Mz+HtSy0uAS4lBNKtTg cda0dwZbqpghQ== Date: Wed, 17 Apr 2024 14:14:04 +0100 From: Simon Horman To: Eric Dumazet Cc: "David S. Miller" , Jakub Kicinski , Paolo Abeni , Jamal Hadi Salim , Cong Wang , Jiri Pirko , netdev@vger.kernel.org, eric.dumazet@gmail.com Subject: Re: [PATCH net-next 04/14] net_sched: sch_choke: implement lockless choke_dump() Message-ID: <20240417131404.GX2320920@kernel.org> References: <20240415132054.3822230-1-edumazet@google.com> <20240415132054.3822230-5-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240415132054.3822230-5-edumazet@google.com> On Mon, Apr 15, 2024 at 01:20:44PM +0000, Eric Dumazet wrote: > Instead of relying on RTNL, choke_dump() can use READ_ONCE() > annotations, paired with WRITE_ONCE() ones in choke_change(). > > Also use READ_ONCE(q->limit) in choke_enqueue() as the value > could change from choke_change(). Hi Eric, I'm wondering if you could expand on why q->limit needs this treatment but not other fields, f.e. q->parms.qth_min (aka p->qth_min). > Signed-off-by: Eric Dumazet > --- > include/net/red.h | 10 +++++----- > net/sched/sch_choke.c | 23 ++++++++++++----------- > 2 files changed, 17 insertions(+), 16 deletions(-) > > diff --git a/include/net/red.h b/include/net/red.h ... > @@ -244,7 +244,7 @@ static inline void red_set_parms(struct red_parms *p, > max_P = red_maxp(Plog); > max_P *= delta; /* max_P = (qth_max - qth_min)/2^Plog */ > } > - p->max_P = max_P; > + WRITE_ONCE(p->max_P, max_P); > max_p_delta = max_P / delta; > max_p_delta = max(max_p_delta, 1U); > p->max_P_reciprocal = reciprocal_value(max_p_delta); A little further down in this function p->Scell_log is set. I think it also needs the WRITE_ONCE() treatment as it is read in choke_dump(). > diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c ... > @@ -431,15 +431,16 @@ static int choke_init(struct Qdisc *sch, struct nlattr *opt, > static int choke_dump(struct Qdisc *sch, struct sk_buff *skb) > { > struct choke_sched_data *q = qdisc_priv(sch); > + u8 Wlog = READ_ONCE(q->parms.Wlog); > struct nlattr *opts = NULL; > struct tc_red_qopt opt = { > - .limit = q->limit, > - .flags = q->flags, > - .qth_min = q->parms.qth_min >> q->parms.Wlog, > - .qth_max = q->parms.qth_max >> q->parms.Wlog, > - .Wlog = q->parms.Wlog, > - .Plog = q->parms.Plog, > - .Scell_log = q->parms.Scell_log, > + .limit = READ_ONCE(q->limit), > + .flags = READ_ONCE(q->flags), > + .qth_min = READ_ONCE(q->parms.qth_min) >> Wlog, > + .qth_max = READ_ONCE(q->parms.qth_max) >> Wlog, > + .Wlog = Wlog, > + .Plog = READ_ONCE(q->parms.Plog), > + .Scell_log = READ_ONCE(q->parms.Scell_log), > }; > > opts = nla_nest_start_noflag(skb, TCA_OPTIONS);