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From: Paolo Abeni <pabeni@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
	Jamal Hadi Salim <jhs@mojatatu.com>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	Jiri Pirko <jiri@resnulli.us>,
	John Fastabend <john.fastabend@gmail.com>
Subject: Re: [PATCH net-next 2/2] pfifo_fast: drop unneeded additional lock on dequeue
Date: Wed, 16 May 2018 09:56:16 +0200	[thread overview]
Message-ID: <1526457376.2553.1.camel@redhat.com> (raw)
In-Reply-To: <20180515221013-mutt-send-email-mst@kernel.org>

On Tue, 2018-05-15 at 23:17 +0300, Michael S. Tsirkin wrote:
> On Tue, May 15, 2018 at 04:24:37PM +0200, Paolo Abeni wrote:
> > After the previous patch, for NOLOCK qdiscs, q->seqlock is
> > always held when the dequeue() is invoked, we can drop
> > any additional locking to protect such operation.
> > 
> > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> > ---
> >  include/linux/skb_array.h | 5 +++++
> >  net/sched/sch_generic.c   | 4 ++--
> >  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> Is the seqlock taken during qdisc_change_tx_queue_len?
> We need to prevent that racing with dequeue.

Thanks for the head-up! I missed that code-path.

I'll add the lock in qdisc_change_tx_queue_len() in v2.

Thanks you,

Paolo

  reply	other threads:[~2018-05-16  7:56 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-15 14:24 [PATCH net-next 0/2] sched: refactor NOLOCK qdiscs Paolo Abeni
2018-05-15 14:24 ` [PATCH net-next 1/2] sched: replace __QDISC_STATE_RUNNING bit with a spin lock Paolo Abeni
2018-05-15 14:24 ` [PATCH net-next 2/2] pfifo_fast: drop unneeded additional lock on dequeue Paolo Abeni
2018-05-15 20:17   ` Michael S. Tsirkin
2018-05-16  7:56     ` Paolo Abeni [this message]
2018-05-16  9:57       ` Paolo Abeni
2018-05-16 14:24       ` Michael S. Tsirkin
2018-05-17 17:06 ` [PATCH net-next 0/2] sched: refactor NOLOCK qdiscs David Miller

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