RE: [PATCH net] driver: e1000: fix race condition between e1000_down() and e1000_watchdog

[Brown, Aaron F]

> From: netdev-owner@xxxxxxxxxxxxxxx [mailto:netdev-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Vincenzo Maffione
> Sent: Saturday, September 16, 2017 9:00 AM
> To: Kirsher, Jeffrey T <jeffrey.t.kirsher@xxxxxxxxx>
> Cc: intel-wired-lan@xxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Vincenzo Maffione <v.maffione@xxxxxxxxx>
> Subject: [PATCH net] driver: e1000: fix race condition between e1000_down()
> and e1000_watchdog
> 
> This patch fixes a race condition that can result into the interface being
> up and carrier on, but with transmits disabled in the hardware.
> The bug may show up by repeatedly IFF_DOWN+IFF_UP the interface, which
> allows e1000_watchdog() interleave with e1000_down().
> 
>     CPU x                           CPU y
>     --------------------------------------------------------------------
>     e1000_down():
>         netif_carrier_off()
>                                     e1000_watchdog():
>                                         if (carrier == off) {
>                                             netif_carrier_on();
>                                             enable_hw_transmit();
>                                         }
>         disable_hw_transmit();
>                                     e1000_watchdog():
>                                         /* carrier on, do nothing */
> 
> Signed-off-by: Vincenzo Maffione <v.maffione@xxxxxxxxx>
> ---
>  drivers/net/ethernet/intel/e1000/e1000_main.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)

Tested-by: Aaron Brown <aaron.f.brown@xxxxxxxxx>