Patch "e1000e: Separate signaling for link check/link up" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

e1000e: Separate signaling for link check/link up

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
e1000e-separate-signaling-for-link-check-link-up.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Benjamin Poirier <[email protected]>
Date: Fri, 21 Jul 2017 11:36:26 -0700
Subject: e1000e: Separate signaling for link check/link up

From: Benjamin Poirier <[email protected]>

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().

---
 drivers/net/ethernet/intel/e1000e/mac.c    |   11 ++++++++---
 drivers/net/ethernet/intel/e1000e/netdev.c |    2 +-
 2 files changed, 9 insertions(+), 4 deletions(-)

@@ -410,6 +410,9 @@ void e1000e_clear_hw_cntrs_base(struct e
  *  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
 	 * 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
 	 * 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;
 }
 
 /**

@@ -5017,7 +5017,7 @@ static bool e1000e_has_link(struct e1000
 	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;
 		}

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/e1000e-fix-error-path-in-link-detection.patch queue-4.4/e1000e-separate-signaling-for-link-check-link-up.patch queue-4.4/e1000e-fix-return-value-test.patch