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

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Message-ID:
 <PH0PR18MB473488467A2026CA30916528C7102@PH0PR18MB4734.namprd18.prod.outlook.com>
Date: Mon, 6 Jan 2025 05:57:09 +0000
From: Shinas Rasheed <srasheed@...vell.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Haseeb Gani
	<hgani@...vell.com>, Sathesh B Edara <sedara@...vell.com>,
        Vimlesh Kumar
	<vimleshk@...vell.com>,
        "thaller@...hat.com" <thaller@...hat.com>,
        "wizhao@...hat.com" <wizhao@...hat.com>,
        "kheib@...hat.com"
	<kheib@...hat.com>,
        "konguyen@...hat.com" <konguyen@...hat.com>,
        "horms@...nel.org" <horms@...nel.org>,
        "einstein.xue@...axg.com"
	<einstein.xue@...axg.com>,
        Veerasenareddy Burru <vburru@...vell.com>,
        Andrew
 Lunn <andrew+netdev@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Eric
 Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
        Abhijit
 Ayarekar <aayarekar@...vell.com>,
        Satananda Burla <sburla@...vell.com>
Subject: RE: [EXTERNAL] Re: [PATCH net v4 1/4] octeon_ep: fix race conditions
 in ndo_get_stats64

Hi Jakub,

> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Saturday, January 4, 2025 10:31 PM
> To: Shinas Rasheed <srasheed@...vell.com>
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Haseeb Gani
> <hgani@...vell.com>; Sathesh B Edara <sedara@...vell.com>; Vimlesh
> Kumar <vimleshk@...vell.com>; thaller@...hat.com; wizhao@...hat.com;
> kheib@...hat.com; konguyen@...hat.com; horms@...nel.org;
> einstein.xue@...axg.com; Veerasenareddy Burru <vburru@...vell.com>;
> Andrew Lunn <andrew+netdev@...n.ch>; David S. Miller
> <davem@...emloft.net>; Eric Dumazet <edumazet@...gle.com>; Paolo
> Abeni <pabeni@...hat.com>; Abhijit Ayarekar <aayarekar@...vell.com>;
> Satananda Burla <sburla@...vell.com>
> Subject: [EXTERNAL] Re: [PATCH net v4 1/4] octeon_ep: fix race conditions in
> ndo_get_stats64
> 
> On Thu, 2 Jan 2025 03: 22: 43 -0800 Shinas Rasheed wrote: > diff --git
> a/drivers/net/ethernet/marvell/octeon_ep/octep_main. c
> b/drivers/net/ethernet/marvell/octeon_ep/octep_main. c > index
> 549436efc204. . a452ee3b9a98 100644 > ---
> a/drivers/net/ethernet/marvell/octeon_ep/octep_main. c
> On Thu, 2 Jan 2025 03:22:43 -0800 Shinas Rasheed wrote:
> > diff --git a/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> b/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> > index 549436efc204..a452ee3b9a98 100644
> > --- a/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> > +++ b/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> > @@ -995,16 +995,14 @@ static void octep_get_stats64(struct net_device
> *netdev,
> >  	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 ?

> --
> pw-bot: cr