4.4-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 44c445c3d1b4eacff23141fa7977c3b2ec3a45c9 ]
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@gmail.com Tested-by: Aaron Brown aaron.f.brown@intel.com Signed-off-by: Jeff Kirsher jeffrey.t.kirsher@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/intel/e1000/e1000_main.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c index 2a1d4a9d3c19..1f84f2fa459f 100644 --- a/drivers/net/ethernet/intel/e1000/e1000_main.c +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c @@ -521,8 +521,6 @@ void e1000_down(struct e1000_adapter *adapter) struct net_device *netdev = adapter->netdev; u32 rctl, tctl;
- netif_carrier_off(netdev); - /* disable receives in the hardware */ rctl = er32(RCTL); ew32(RCTL, rctl & ~E1000_RCTL_EN); @@ -538,6 +536,15 @@ void e1000_down(struct e1000_adapter *adapter) E1000_WRITE_FLUSH(); msleep(10);
+ /* Set the carrier off after transmits have been disabled in the + * hardware, to avoid race conditions with e1000_watchdog() (which + * may be running concurrently to us, checking for the carrier + * bit to decide whether it should enable transmits again). Such + * a race condition would result into transmission being disabled + * in the hardware until the next IFF_DOWN+IFF_UP cycle. + */ + netif_carrier_off(netdev); + napi_disable(&adapter->napi);
e1000_irq_disable(adapter);