linux-kernel - RE: [Intel-wired-lan] [PATCH 4/5] e1000e: Separate signaling for link check/link up

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Message-ID: <309B89C4C689E141A5FF6A0C5FB2118B8C6A05C9@ORSMSX101.amr.corp.intel.com>
Date:   Fri, 15 Sep 2017 00:27:46 +0000
From:   "Brown, Aaron F" <aaron.f.brown@...el.com>
To:     Benjamin Poirier <bpoirier@...e.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Lennart Sorensen" <lsorense@...lub.uwaterloo.ca>
Subject: RE: [Intel-wired-lan] [PATCH 4/5] e1000e: Separate signaling for
 link check/link up


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@...lub.uwaterloo.ca>
> Signed-off-by: Benjamin Poirier <bpoirier@...e.com>
> ---
>   drivers/net/ethernet/intel/e1000e/mac.c    | 11 ++++++++---
>   drivers/net/ethernet/intel/e1000e/netdev.c |  2 +-
>   2 files changed, 9 insertions(+), 4 deletions(-)

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