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 05D65171675 for ; Wed, 17 Apr 2024 17:22:48 +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=1713374569; cv=none; b=TyGGTmg3qK3/aLBoVp3z7y/dXwBwQl5aQRwOUZMEKtOfxPTkcDdCMUNIisPt7cPp5QSSWVuh5pUAqASjRNN7rBhiouddeO3CEjRXclTWgiy2tTcFUHtl4vSc8v1w+xXNYfQW6O+M4xfptDkiIu8wZ50ni28ba17nA0SdTuXrg/4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713374569; c=relaxed/simple; bh=gIqsgJfSyaKqmfdIEmBsxi00/+lqM5htyVgYrc6d7Pk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TjxYKRH7OTfwQAeErbqf5WmdywBrDl2JdGpUAy5c3VNmZwZ56I3y/FQWy0dV/1UYedDVwEeQX3AjrSgmepH6iJUi3KBA2zxkWyDxfBpzqGMfNK+c3ykIXR3GcvHHvkweP3AfXzXhhGvtaLIG+LeUULPyeKKHrSj0MsEP39F8Mek= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kBvDDuBT; 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="kBvDDuBT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB2E8C072AA; Wed, 17 Apr 2024 17:22:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713374568; bh=gIqsgJfSyaKqmfdIEmBsxi00/+lqM5htyVgYrc6d7Pk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kBvDDuBTt4l03qFCVENrQPBitDmdVd1/WIcUMTI9VXuYhQ63/EGqchgzx7NoPLdbB rbH63JhNIlic9kMiajdIsspeNpcXAUTh4//wfpu4XC4QpKzyyZjLpsliEa8pcvvaiE KepFDTymLF+FPPKVswzihshFKr1kT6Bs1nMNd67ET1vowvfwKCVsNDfVVvu3oNiCQR OUaTH92R4fpe1RY2yrqIgN3w3PSfxQiyEMI+Z4aFk25VGO5YvYSHcZ8yLxzfte9J7J 9GCDpzpXQMPHDcxz6lPHQzLXTneOUxgtWe2BErHRIaApVBt4HSN6mVTI+7emTrBUle WaSP+1jfWcuUA== Date: Wed, 17 Apr 2024 18:22:44 +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 09/14] net_sched: sch_fq_codel: implement lockless fq_codel_dump() Message-ID: <20240417172244.GH2320920@kernel.org> References: <20240415132054.3822230-1-edumazet@google.com> <20240415132054.3822230-10-edumazet@google.com> <20240417170739.GE2320920@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Apr 17, 2024 at 07:14:10PM +0200, Eric Dumazet wrote: > On Wed, Apr 17, 2024 at 7:07 PM Simon Horman wrote: > > > > On Mon, Apr 15, 2024 at 01:20:49PM +0000, Eric Dumazet wrote: > > > Instead of relying on RTNL, fq_codel_dump() can use READ_ONCE() > > > annotations, paired with WRITE_ONCE() ones in fq_codel_change(). > > > > > > Signed-off-by: Eric Dumazet > > > --- > > > net/sched/sch_fq_codel.c | 57 ++++++++++++++++++++++++---------------- > > > 1 file changed, 35 insertions(+), 22 deletions(-) > > > > > > diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c > > > > ... > > > > > @@ -529,30 +539,33 @@ static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb) > > > goto nla_put_failure; > > > > > > if (nla_put_u32(skb, TCA_FQ_CODEL_TARGET, > > > - codel_time_to_us(q->cparams.target)) || > > > + codel_time_to_us(READ_ONCE(q->cparams.target))) || > > > nla_put_u32(skb, TCA_FQ_CODEL_LIMIT, > > > - sch->limit) || > > > + READ_ONCE(sch->limit)) || > > > nla_put_u32(skb, TCA_FQ_CODEL_INTERVAL, > > > - codel_time_to_us(q->cparams.interval)) || > > > + codel_time_to_us(READ_ONCE(q->cparams.interval))) || > > > nla_put_u32(skb, TCA_FQ_CODEL_ECN, > > > - q->cparams.ecn) || > > > + READ_ONCE(q->cparams.ecn)) || > > > nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM, > > > - q->quantum) || > > > + READ_ONCE(q->quantum)) || > > > nla_put_u32(skb, TCA_FQ_CODEL_DROP_BATCH_SIZE, > > > - q->drop_batch_size) || > > > + READ_ONCE(q->drop_batch_size)) || > > > nla_put_u32(skb, TCA_FQ_CODEL_MEMORY_LIMIT, > > > - q->memory_limit) || > > > + READ_ONCE(q->memory_limit)) || > > > nla_put_u32(skb, TCA_FQ_CODEL_FLOWS, > > > - q->flows_cnt)) > > > + READ_ONCE(q->flows_cnt))) > > > > Hi Eric, > > > > I think you missed the corresponding update for q->flows_cnt > > in fq_codel_change(). > > q->flows_cnt is set at init time only, it can not change yet. Sorry, I missed that important detail. > Blindly using READ_ONCE() in a dump seems good hygiene, > it is not needed yet, but does no harm. Thanks, understood. Reviewed-by: Simon Horman