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Message-ID: <20240206072114.244738a9@kernel.org>
Date: Tue, 6 Feb 2024 07:21:14 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Shinas Rasheed <srasheed@...vell.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Haseeb Gani
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Brett Creeley <brett.creeley@....com>, Andrew Lunn <andrew@...n.ch>, Jacob
Keller <jacob.e.keller@...el.com>
Subject: Re: [EXT] Re: [PATCH net-next v5 1/8] octeon_ep_vf: Add driver
framework and device initialization
On Tue, 6 Feb 2024 07:42:12 +0000 Shinas Rasheed wrote:
> > > We do cancel_work_sync in octep_vf_remove function.
> >
> > But the device is still registered, so the timeout can happen after you
> > cancel but before you unregister.
>
> There is rtnl_lock inside octep_vf_tx_timeout_task (the work task
> function), which can protect from unregister_netdev, for such cases
> (code snippet for quick reference below):
>
> static void octep_vf_tx_timeout_task(struct work_struct *work)
> {
> struct octep_vf_device *oct = container_of(work, struct octep_vf_device, tx_timeout_task);
> struct net_device *netdev = oct->netdev;
>
> rtnl_lock();
> if (netif_running(netdev)) {
> octep_vf_stop(netdev);
> octep_vf_open(netdev);
> }
> rtnl_unlock();
> }
>
> I hope this takes care of it? Please let me know if my thought
> process feels wrong. Thanks!
The problem I see is that if the queue is somehow overloaded or delayed
there can be a race where we cancel, then timeout happens, work doesn't
run for a while, and we free the netdev. So what I'm suggesting is -
hold a reference on the netdevice. That way you can be sure it doesn't
get freed and you can depend on the rtnl+netif_running() doing its job.
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