netdev - RE: [PATCH 2/2] e1000e: Fix link check race condition

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Date:   Sat, 10 Mar 2018 04:53:31 +0000
From:   "Brown, Aaron F" <aaron.f.brown@...el.com>
To:     Benjamin Poirier <bpoirier@...e.com>,
        "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>
CC:     Alexander Duyck <alexander.duyck@...il.com>,
        Lennart Sorensen <lsorense@...lub.uwaterloo.ca>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/2] e1000e: Fix link check race condition

> From: netdev-owner@...r.kernel.org [mailto:netdev-
> owner@...r.kernel.org] On Behalf Of Benjamin Poirier
> Sent: Monday, March 5, 2018 5:56 PM
> To: Kirsher, Jeffrey T <jeffrey.t.kirsher@...el.com>
> Cc: Alexander Duyck <alexander.duyck@...il.com>; Lennart Sorensen
> <lsorense@...lub.uwaterloo.ca>; intel-wired-lan@...ts.osuosl.org;
> netdev@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [PATCH 2/2] e1000e: Fix link check race condition
> 
> Alex reported the following race condition:
> 
> /* link goes up... interrupt... schedule watchdog */
> \ e1000_watchdog_task
> 	\ e1000e_has_link
> 		\ hw->mac.ops.check_for_link() ===
> e1000e_check_for_copper_link
> 			\ e1000e_phy_has_link_generic(..., &link)
> 				link = true
> 
> 					 /* link goes down... interrupt */
> 					 \ e1000_msix_other
> 						 hw->mac.get_link_status =
> true
> 
> 			/* link is up */
> 			mac->get_link_status = false
> 
> 		link_active = true
> 		/* link_active is true, wrongly, and stays so because
> 		 * get_link_status is false */
> 
> Avoid this problem by making sure that we don't set get_link_status = false
> after having checked the link.
> 
> It seems this problem has been present since the introduction of e1000e.
> 
> Link: https://lkml.org/lkml/2018/1/29/338
> Reported-by: Alexander Duyck <alexander.duyck@...il.com>
> Signed-off-by: Benjamin Poirier <bpoirier@...e.com>
> ---
>  drivers/net/ethernet/intel/e1000e/ich8lan.c | 31 ++++++++++++++++-------
> ------
>  drivers/net/ethernet/intel/e1000e/mac.c     | 14 ++++++-------
>  2 files changed, 24 insertions(+), 21 deletions(-)

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