e1000e: Separate signaling for link check/link up

commit 19110cfbb34d4af0cdfe14cd243f3b09dc95b013 upstream.

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>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/net/ethernet/intel/e1000e/lib.c b/drivers/net/ethernet/intel/e1000e/lib.c
index 0893ab1..8224a12 100644 (file)
--- a/drivers/net/ethernet/intel/e1000e/lib.c
+++ b/drivers/net/ethernet/intel/e1000e/lib.c
@@ -435,6 +435,9 @@ 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)
 {
@@ -449,7 +452,7 @@ 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
@@ -494,10 +497,12 @@ 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 a783530..73cc0f6 100644 (file)
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -4222,7 +4222,7 @@ 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 = 1;
                }