From: Jakub Kicinski <kuba@kernel.org>
To: Joe Damato <jdamato@fastly.com>
Cc: netdev@vger.kernel.org, gerhard@engleder-embedded.com,
jasowang@redhat.com, leiyang@redhat.com,
xuanzhuo@linux.alibaba.com, mkarsten@uwaterloo.ca,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
Kuniyuki Iwashima <kuniyu@amazon.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Lorenzo Bianconi <lorenzo@kernel.org>,
Alexander Lobakin <aleksander.lobakin@intel.com>,
linux-kernel@vger.kernel.org (open list)
Subject: Re: [RFC net-next v3 1/4] net: protect queue -> napi linking with netdev_lock()
Date: Mon, 27 Jan 2025 13:37:56 -0800 [thread overview]
Message-ID: <20250127133756.413efb24@kernel.org> (raw)
In-Reply-To: <20250121191047.269844-2-jdamato@fastly.com>
On Tue, 21 Jan 2025 19:10:41 +0000 Joe Damato wrote:
> From: Jakub Kicinski <kuba@kernel.org>
>
> netdev netlink is the only reader of netdev_{,rx_}queue->napi,
> and it already holds netdev->lock. Switch protection of the
> writes to netdev->lock as well.
>
> Add netif_queue_set_napi_locked() for API completeness,
> but the expectation is that most current drivers won't have
> to worry about locking any more. Today they jump thru hoops
> to take rtnl_lock.
I started having second thoughts about this patch, sorry to say.
NAPI objects were easy to protect with the lock because there's
a clear registration and unregistration API. Queues OTOH are made
visible by the netif_set_real_num_queues() call, which is tricky
to protect with the instance lock. Queues are made visible, then
we configure them.
My thinking changed a bit, I think we should aim to protect all
ndos and ethtool ops with the instance lock. Stanislav and Saeed
seem to be working on that:
https://lore.kernel.org/all/Z5LhKdNMO5CvAvZf@mini-arch/
so hopefully that doesn't cause too much of a delay.
But you may need to rework this series further :(
next prev parent reply other threads:[~2025-01-27 21:37 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-21 19:10 [RFC net-next v3 0/4] virtio_net: Link queues to NAPIs Joe Damato
2025-01-21 19:10 ` [RFC net-next v3 1/4] net: protect queue -> napi linking with netdev_lock() Joe Damato
2025-01-27 21:37 ` Jakub Kicinski [this message]
2025-01-27 22:21 ` Joe Damato
2025-01-21 19:10 ` [RFC net-next v3 2/4] virtio_net: Prepare for NAPI to queue mapping Joe Damato
2025-01-22 6:12 ` Jason Wang
2025-01-22 17:40 ` Joe Damato
2025-01-23 2:40 ` Jason Wang
2025-01-23 2:47 ` Joe Damato
2025-01-24 1:14 ` Jason Wang
2025-01-24 20:19 ` Joe Damato
2025-01-26 8:04 ` Jason Wang
2025-01-27 17:52 ` Joe Damato
2025-01-27 19:31 ` Joe Damato
2025-01-27 21:33 ` Jakub Kicinski
2025-01-27 22:07 ` Joe Damato
2025-01-27 22:24 ` Jakub Kicinski
2025-01-27 22:32 ` Joe Damato
2025-01-21 19:10 ` [RFC net-next v3 3/4] virtio_net: Map NAPIs to queues Joe Damato
2025-01-21 20:13 ` Gerhard Engleder
2025-01-22 6:13 ` Jason Wang
2025-01-21 19:10 ` [RFC net-next v3 4/4] virtio_net: Use persistent NAPI config Joe Damato
2025-01-21 20:18 ` Gerhard Engleder
2025-01-22 6:13 ` Jason Wang
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