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Subject[PATCH 4.4 71/96] e1000e: Separate signaling for link check/link up
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Benjamin Poirier <bpoirier@suse.com>

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>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/net/ethernet/intel/e1000e/mac.c
+++ b/drivers/net/ethernet/intel/e1000e/mac.c
@@ -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;
}

/**
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -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;
}

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