netdev - RE: [PATCH net] ice: Fix race condition during interface enslave

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Date:   Thu, 10 Mar 2022 19:26:02 +0000
From:   "Ertman, David M" <david.m.ertman@...el.com>
To:     Ivan Vecera <ivecera@...hat.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Petr Oros <poros@...hat.com>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net] ice: Fix race condition during interface enslave

> -----Original Message-----
> From: Ivan Vecera <ivecera@...hat.com>
> Sent: Thursday, March 10, 2022 10:07 AM
> To: Ertman, David M <david.m.ertman@...el.com>
> Cc: netdev@...r.kernel.org; Petr Oros <poros@...hat.com>; Brandeburg,
> Jesse <jesse.brandeburg@...el.com>; Nguyen, Anthony L
> <anthony.l.nguyen@...el.com>; David S. Miller <davem@...emloft.net>;
> Jakub Kicinski <kuba@...nel.org>; moderated list:INTEL ETHERNET DRIVERS"
> <intel-wired-lan@...ts.osuosl.org>, open list <linux-kernel@...r.kernel.org>
> Subject: Re: [PATCH net] ice: Fix race condition during interface enslave
> 
> On Thu, 10 Mar 2022 17:48:16 +0000
> "Ertman, David M" <david.m.ertman@...el.com> wrote:
> 
> > This only addresses one case of unplugging the auxiliary bus.  Rather than
> controlling one instance of
> > calling ice_unplig_aux_dev(), it seems like it would be better to modify
> ice_unplug_aux_dev so that it
> > will pause until any plugging is done by the service task (check for the pf-
> >flag bit and wait until it clears
> > before progressing).
> 
> You cannot wait in ice_unplug_aux_dev() for ICE_FLAG_PLUG_AUX_DEV to
> be cleared because
> ice_clear_rdma_cap() is called under RTNL.
> This patch is a counter part for commit 5dbbbd01cbba83 ("ice: Avoid RTNL
> lock when
> re-creating auxiliary device") that eliminates ice_plug_aux() and fixed first
> part
> of deadlock and this patch fixes a second part and eliminates also
> ice_unplug_aux_dev()
> to be called under RTNL.
> 
> Thanks,
> Ivan

You are correct.  I forgot about the RTNL context!

With this in mind - I agree with your approach.

Reviewed-by: Dave Ertman <david.m.ertman@...el.com>