linux-kernel - Re: [RFC iwl-net] e1000: Hold RTNL when e1000

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Message-ID: <ZxgEb0N0cJt1BRte@LQ3V64L9R2>
Date: Tue, 22 Oct 2024 13:00:47 -0700
From: Joe Damato <jdamato@...tly.com>
To: netdev@...r.kernel.org
Cc: dmantipov@...dex.ru, Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	"moderated list:INTEL ETHERNET DRIVERS" <intel-wired-lan@...ts.osuosl.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC iwl-net] e1000: Hold RTNL when e1000_down can be called

On Tue, Oct 22, 2024 at 05:21:53PM +0000, Joe Damato wrote:
> e1000_down calls netif_queue_set_napi, which assumes that RTNL is held.
> 
> There are a few paths for e1000_down to be called in e1000 where RTNL is
> not currently being held:
>   - e1000_shutdown (pci shutdown)
>   - e1000_suspend (power management)
>   - e1000_reinit_locked (via e1000_reset_task delayed work)
> 
> Hold RTNL in two places to fix this issue:
>   - e1000_reset_task
>   - __e1000_shutdown (which is called from both e1000_shutdown and
>     e1000_suspend).

It looks like there's one other spot I missed:

e1000_io_error_detected (pci error handler) which should also hold
rtnl_lock:

+       if (netif_running(netdev)) {
+               rtnl_lock();
                e1000_down(adapter);
+               rtnl_unlock();
+       }

I can send that update in the v2, but I'll wait to see if Intel has suggestions
on the below.
 
> The other paths which call e1000_down seemingly hold RTNL and are OK:
>   - e1000_close (ndo_stop)
>   - e1000_change_mtu (ndo_change_mtu)
> 
> I'm submitting this is as an RFC because:
>   - the e1000_reinit_locked issue appears very similar to commit
>     21f857f0321d ("e1000e: add rtnl_lock() to e1000_reset_task"), which
>     fixes a similar issue in e1000e
> 
> however
> 
>   - adding rtnl to e1000_reinit_locked seemingly conflicts with an
>     earlier e1000 commit b2f963bfaeba ("e1000: fix lockdep warning in
>     e1000_reset_task").
> 
> Hopefully Intel can weigh in and shed some light on the correct way to
> go.
> 
> Fixes: 8f7ff18a5ec7 ("e1000: Link NAPI instances to queues and IRQs")
> Reported-by: Dmitry Antipov <dmantipov@...dex.ru>
> Closes: https://lore.kernel.org/netdev/8cf62307-1965-46a0-a411-ff0080090ff9@yandex.ru/
> Signed-off-by: Joe Damato <jdamato@...tly.com>