target/linux/generic/pending-4.9/190-4-5-e1000e-Separate-signaling-for-link-check-link-up.patch

   1 From patchwork Fri Jul 21 18:36:26 2017
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   5 Subject: [4/5] e1000e: Separate signaling for link check/link up
   6 From: Benjamin Poirier <bpoirier@suse.com>
   7 X-Patchwork-Id: 9857491
   8 Message-Id: <20170721183627.13373-4-bpoirier@suse.com>
   9 To: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
  10 Cc: Lennart Sorensen <lsorense@csclub.uwaterloo.ca>,
  11  intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
  12  linux-kernel@vger.kernel.org
  13 Date: Fri, 21 Jul 2017 11:36:26 -0700
  14
  15 Lennart reported the following race condition:
  16
  17 \ e1000_watchdog_task
  18     \ e1000e_has_link
  19         \ hw->mac.ops.check_for_link() === e1000e_check_for_copper_link
  20             /* link is up */
  21             mac->get_link_status = false;
  22
  23                             /* interrupt */
  24                             \ e1000_msix_other
  25                                 hw->mac.get_link_status = true;
  26
  27         link_active = !hw->mac.get_link_status
  28         /* link_active is false, wrongly */
  29
  30 This problem arises because the single flag get_link_status is used to
  31 signal two different states: link status needs checking and link status is
  32 down.
  33
  34 Avoid the problem by using the return value of .check_for_link to signal
  35 the link status to e1000e_has_link().
  36
  37 Reported-by: Lennart Sorensen <lsorense@csclub.uwaterloo.ca>
  38 Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
  39 ---
  40  drivers/net/ethernet/intel/e1000e/mac.c    | 11 ++++++++---
  41  drivers/net/ethernet/intel/e1000e/netdev.c |  2 +-
  42  2 files changed, 9 insertions(+), 4 deletions(-)
  43
  44 --- a/drivers/net/ethernet/intel/e1000e/mac.c
  45 +++ b/drivers/net/ethernet/intel/e1000e/mac.c
  46 @@ -410,6 +410,9 @@ void e1000e_clear_hw_cntrs_base(struct e
  47   *  Checks to see of the link status of the hardware has changed.  If a
  48   *  change in link status has been detected, then we read the PHY registers
  49   *  to get the current speed/duplex if link exists.
  50 + *
  51 + *  Returns a negative error code (-E1000_ERR_*) or 0 (link down) or 1 (link
  52 + *  up).
  53   **/
  54  s32 e1000e_check_for_copper_link(struct e1000_hw *hw)
  55  {
  56 @@ -423,7 +426,7 @@ s32 e1000e_check_for_copper_link(struct
  57          * Change or Rx Sequence Error interrupt.
  58          */
  59         if (!mac->get_link_status)
  60 -               return 0;
  61 +               return 1;
  62
  63         /* First we want to see if the MII Status Register reports
  64          * link.  If so, then we want to get the current speed/duplex
  65 @@ -461,10 +464,12 @@ s32 e1000e_check_for_copper_link(struct
  66          * different link partner.
  67          */
  68         ret_val = e1000e_config_fc_after_link_up(hw);
  69 -       if (ret_val)
  70 +       if (ret_val) {
  71                 e_dbg("Error configuring flow control\n");
  72 +               return ret_val;
  73 +       }
  74
  75 -       return ret_val;
  76 +       return 1;
  77  }
  78
  79  /**
  80 --- a/drivers/net/ethernet/intel/e1000e/netdev.c
  81 +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
  82 @@ -5056,7 +5056,7 @@ static bool e1000e_has_link(struct e1000
  83         case e1000_media_type_copper:
  84                 if (hw->mac.get_link_status) {
  85                         ret_val = hw->mac.ops.check_for_link(hw);
  86 -                       link_active = !hw->mac.get_link_status;
  87 +                       link_active = ret_val > 0;
  88                 } else {
  89                         link_active = true;
  90                 }