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Date:   Mon, 29 Aug 2022 18:29:29 +0200
From:   Ivan Vecera <ivecera@redhat.com>
To:     "Laba, SlawomirX" <slawomirx.laba@intel.com>
Cc:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "Keller, Jacob E" <jacob.e.keller@intel.com>,
        "Piotrowski, Patryk" <patryk.piotrowski@intel.com>,
        Vitaly Grinberg <vgrinber@redhat.com>,
        "Brandeburg, Jesse" <jesse.brandeburg@intel.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@intel.com>,
        "David S. Miller" <davem@davemloft.net>,
        "Eric Dumazet" <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
        "moderated list:INTEL ETHERNET DRIVERS" 
        <intel-wired-lan@lists.osuosl.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net] iavf: Detach device during reset task
Message-ID: <20220829182929.2822fafc@p1.luc.cera.cz>
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On Mon, 22 Aug 2022 17:42:44 +0000
"Laba, SlawomirX" <slawomirx.laba@intel.com> wrote:

> > -----Original Message-----
> > From: ivecera <ivecera@redhat.com>
> > Sent: Thursday, August 18, 2022 6:56 PM
> > To: netdev@vger.kernel.org
> > Cc: Keller, Jacob E <jacob.e.keller@intel.com>; Piotrowski, Patryk
> > <patryk.piotrowski@intel.com>; Vitaly Grinberg <vgrinber@redhat.com>;
> > Brandeburg, Jesse <jesse.brandeburg@intel.com>; Nguyen, Anthony L
> > <anthony.l.nguyen@intel.com>; David S. Miller <davem@davemloft.net>; Eric
> > Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo
> > Abeni <pabeni@redhat.com>; Jeff Kirsher <jeffrey.t.kirsher@intel.com>;
> > moderated list:INTEL ETHERNET DRIVERS <intel-wired-lan@lists.osuosl.org>;
> > open list <linux-kernel@vger.kernel.org>
> > Subject: [PATCH net] iavf: Detach device during reset task
> > 
> > iavf_reset_task() takes crit_lock at the beginning and holds it during whole call.
> > The function subsequently calls
> > iavf_init_interrupt_scheme() that grabs RTNL. Problem occurs when userspace
> > initiates during the reset task any ndo callback that runs under RTNL like
> > iavf_open() because some of that functions tries to take crit_lock. This leads to
> > classic A-B B-A deadlock scenario.
> > 
> > To resolve this situation the device should be detached in
> > iavf_reset_task() prior taking crit_lock to avoid subsequent ndos running under
> > RTNL and reattach the device at the end.
> > 
> > Fixes: 62fe2a865e6d ("i40evf: add missing rtnl_lock() around
> > i40evf_set_interrupt_capability")
> > Cc: Jacob Keller <jacob.e.keller@intel.com>
> > Cc: Patryk Piotrowski <patryk.piotrowski@intel.com>
> > Tested-by: Vitaly Grinberg <vgrinber@redhat.com>
> > Signed-off-by: Ivan Vecera <ivecera@redhat.com>
> > ---
> >  drivers/net/ethernet/intel/iavf/iavf_main.c | 22 +++++++++++++++------
> >  1 file changed, 16 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/iavf/iavf_main.c
> > b/drivers/net/ethernet/intel/iavf/iavf_main.c
> > index f39440ad5c50..ee8f911b57ea 100644
> > --- a/drivers/net/ethernet/intel/iavf/iavf_main.c
> > +++ b/drivers/net/ethernet/intel/iavf/iavf_main.c
> > @@ -2877,6 +2877,13 @@ static void iavf_reset_task(struct work_struct
> > *work)
> >  	int i = 0, err;
> >  	bool running;
> > 
> > +	/*
> > +	 * Detach interface to avoid subsequent NDO callbacks
> > +	 */  
> 
> nit:
> The comment should start this way: /* Detach ...

Will fix.

> > +	rtnl_lock();
> > +	netif_device_detach(netdev);
> > +	rtnl_unlock();
> > +
> >  	/* When device is being removed it doesn't make sense to run the reset
> >  	 * task, just return in such a case.
> >  	 */
> > @@ -2884,7 +2891,7 @@ static void iavf_reset_task(struct work_struct *work)
> >  		if (adapter->state != __IAVF_REMOVE)
> >  			queue_work(iavf_wq, &adapter->reset_task);
> > 
> > -		return;
> > +		goto reset_finish;  
> 
> Correct me if I'm wrong.
> In case when you fail to grab a crit_lock you'd jump to the reset_finish label and unlock the locks you didn't lock.

You're right.. I tried to dedup mutex unlocks after testing and missed this path.
Will fix by v2.

Thanks,
I.

> >  	}
> > 
> >  	while (!mutex_trylock(&adapter->client_lock))
> > @@ -2954,7 +2961,6 @@ static void iavf_reset_task(struct work_struct *work)
> > 
> >  	if (running) {
> >  		netif_carrier_off(netdev);
> > -		netif_tx_stop_all_queues(netdev);
> >  		adapter->link_up = false;
> >  		iavf_napi_disable_all(adapter);
> >  	}
> > @@ -3081,10 +3087,8 @@ static void iavf_reset_task(struct work_struct
> > *work)
> > 
> >  	adapter->flags &= ~IAVF_FLAG_REINIT_ITR_NEEDED;
> > 
> > -	mutex_unlock(&adapter->client_lock);
> > -	mutex_unlock(&adapter->crit_lock);
> > +	goto reset_finish;
> > 
> > -	return;
> >  reset_err:
> >  	if (running) {
> >  		set_bit(__IAVF_VSI_DOWN, adapter->vsi.state); @@ -3092,9
> > +3096,15 @@ static void iavf_reset_task(struct work_struct *work)
> >  	}
> >  	iavf_disable_vf(adapter);
> > 
> > +	dev_err(&adapter->pdev->dev, "failed to allocate resources during
> > +reinit\n");
> > +
> > +reset_finish:
> >  	mutex_unlock(&adapter->client_lock);
> >  	mutex_unlock(&adapter->crit_lock);
> > -	dev_err(&adapter->pdev->dev, "failed to allocate resources during
> > reinit\n");
> > +
> > +	rtnl_lock();
> > +	netif_device_attach(netdev);
> > +	rtnl_unlock();
> >  }
> > 
> >  /**
> > --
> > 2.35.1  
>