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SubjectRe: [Intel-wired-lan] [PATCH 4/5] e1000e: Separate signaling for link check/link up
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On 7/21/2017 21:36, Benjamin Poirier wrote:
> Lennart reported the following race condition:
>
> \ e1000_watchdog_task
> \ e1000e_has_link
> \ hw->mac.ops.check_for_link() === e1000e_check_for_copper_link
> /* link is up */
> mac->get_link_status = false;
>
> /* interrupt */
> \ e1000_msix_other
> hw->mac.get_link_status = true;
>
> link_active = !hw->mac.get_link_status
> /* link_active is false, wrongly */
>
> This problem arises because the single flag get_link_status is used to
> signal two different states: link status needs checking and link status is
> down.
>
> Avoid the problem by using the return value of .check_for_link to signal
> the link status to e1000e_has_link().
>
> Reported-by: Lennart Sorensen <lsorense@csclub.uwaterloo.ca>
> Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
> ---
> drivers/net/ethernet/intel/e1000e/mac.c | 11 ++++++++---
> drivers/net/ethernet/intel/e1000e/netdev.c | 2 +-
> 2 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/e1000e/mac.c b/drivers/net/ethernet/intel/e1000e/mac.c
> index b322011ec282..f457c5703d0c 100644
> --- a/drivers/net/ethernet/intel/e1000e/mac.c
> +++ b/drivers/net/ethernet/intel/e1000e/mac.c
> @@ -410,6 +410,9 @@ void e1000e_clear_hw_cntrs_base(struct e1000_hw *hw)
> * Checks to see of the link status of the hardware has changed. If a
> * change in link status has been detected, then we read the PHY registers
> * to get the current speed/duplex if link exists.
> + *
> + * Returns a negative error code (-E1000_ERR_*) or 0 (link down) or 1 (link
> + * up).
> **/
> s32 e1000e_check_for_copper_link(struct e1000_hw *hw)
> {
> @@ -423,7 +426,7 @@ s32 e1000e_check_for_copper_link(struct e1000_hw *hw)
> * Change or Rx Sequence Error interrupt.
> */
> if (!mac->get_link_status)
> - return 0;
> + return 1;
>
> /* First we want to see if the MII Status Register reports
> * link. If so, then we want to get the current speed/duplex
> @@ -461,10 +464,12 @@ s32 e1000e_check_for_copper_link(struct e1000_hw *hw)
> * different link partner.
> */
> ret_val = e1000e_config_fc_after_link_up(hw);
> - if (ret_val)
> + if (ret_val) {
> e_dbg("Error configuring flow control\n");
> + return ret_val;
> + }
>
> - return ret_val;
> + return 1;
> }
>
> /**
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index fc6a1d9999b2..5a8ab1136566 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -5081,7 +5081,7 @@ static bool e1000e_has_link(struct e1000_adapter *adapter)
> case e1000_media_type_copper:
> if (hw->mac.get_link_status) {
> ret_val = hw->mac.ops.check_for_link(hw);
> - link_active = !hw->mac.get_link_status;
> + link_active = ret_val > 0;
> } else {
> link_active = true;
> }

Hello Benjamin,

Will this patch fix any serious problem with link indication? Is it
necessary? Can we consider your patch series without 4/5 part?

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