RE: [EXTERNAL] Re: [PATCH net v4 1/4] octeon_ep: fix race conditions in ndo_get_stats64

[Shinas Rasheed]

Hi Jakub,

Thanks for the reply, will revert

> -----Original Message-----
> From: Jakub Kicinski <kuba@xxxxxxxxxx>
> Sent: Tuesday, January 7, 2025 2:27 AM
> To: Shinas Rasheed <srasheed@xxxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Haseeb Gani
> <hgani@xxxxxxxxxxx>; Sathesh B Edara <sedara@xxxxxxxxxxx>; Vimlesh
> Kumar <vimleshk@xxxxxxxxxxx>; thaller@xxxxxxxxxx; wizhao@xxxxxxxxxx;
> kheib@xxxxxxxxxx; konguyen@xxxxxxxxxx; horms@xxxxxxxxxx;
> einstein.xue@xxxxxxxxxx; Veerasenareddy Burru <vburru@xxxxxxxxxxx>;
> Andrew Lunn <andrew+netdev@xxxxxxx>; David S. Miller
> <davem@xxxxxxxxxxxxx>; Eric Dumazet <edumazet@xxxxxxxxxx>; Paolo
> Abeni <pabeni@xxxxxxxxxx>; Abhijit Ayarekar <aayarekar@xxxxxxxxxxx>;
> Satananda Burla <sburla@xxxxxxxxxxx>
> Subject: Re: [EXTERNAL] Re: [PATCH net v4 1/4] octeon_ep: fix race conditions
> in ndo_get_stats64
> 
> On Mon, 6 Jan 2025 05: 57: 09 +0000 Shinas Rasheed wrote: > > > struct
> octep_device *oct = netdev_priv(netdev); > > > int q; > > > > > > - if
> (netif_running(netdev)) > > > - octep_ctrl_net_get_if_stats(oct,
> On Mon, 6 Jan 2025 05:57:09 +0000 Shinas Rasheed wrote:
> > > >  	struct octep_device *oct = netdev_priv(netdev);
> > > >  	int q;
> > > >
> > > > -	if (netif_running(netdev))
> > > > -		octep_ctrl_net_get_if_stats(oct,
> > > > -					    OCTEP_CTRL_NET_INVALID_VFID,
> > > > -					    &oct->iface_rx_stats,
> > > > -					    &oct->iface_tx_stats);
> > > > -
> > > >  	tx_packets = 0;
> > > >  	tx_bytes = 0;
> > > >  	rx_packets = 0;
> > > >  	rx_bytes = 0;
> > > > +
> > > > +	if (!netif_running(netdev))
> > > > +		return;
> > >
> > > So we'll provide no stats when the device is down? That's not correct.
> > > The driver should save the stats from the freed queues (somewhere in
> > > the oct structure). Also please mention how this is synchronized
> > > against netif_running() changing its state, device may get closed while
> > > we're running..
> >
> > I ACK the 'save stats from freed queues and emit out stats when device is
> down'.
> >
> > About the synchronization, the reason I changed to simple netif_running
> check was to avoid
> > locks (as per previous patch version comments). Please do correct me if I'm
> wrong, but isn't the case
> > you mentioned protected by the rtnl_lock held by the netdev stack when it
> calls the ndo_op ?
> 
> I don't see rtnl_lock being taken in the procfs path.
> 
> FWIW I posted a test for the problem you're fixing in octeon,
> since it's relatively common among drivers:
>  https://urldefense.proofpoint.com/v2/url?u=https-
> 3A__lore.kernel.org_20250105011525.1718380-2D1-2Dkuba-
> 40kernel.org&d=DwICAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=1OxLD4y-
> oxrlgQ1rjXgWtmLz1pnaDjD96sDq-
> cKUwK4&m=9gsH3cuOJoFpbgNiQc2gqY6_Cugh5GeBCKFU9mmblsBxpslPW2q
> VVBa1LG7w8qmb&s=-9Gao3oSw4wAp6L8V86hli4Bmqu3Po8jfOqNOtYwL-
> o&e=
> see also:
>  https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_linux-
> 2Dnetdev_nipa_wiki_Running-2Ddriver-
> 2Dtests&d=DwICAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=1OxLD4y-
> oxrlgQ1rjXgWtmLz1pnaDjD96sDq-
> cKUwK4&m=9gsH3cuOJoFpbgNiQc2gqY6_Cugh5GeBCKFU9mmblsBxpslPW2q
> VVBa1LG7w8qmb&s=q8uPNNae_-
> 4ps18BT6XOel9HsYApsxh4IN01HF2_ARw&e=