e1000e: debug contention on NVM SWFLAG

This patch adds a mutex to the e1000e driver that would help
catch any collisions of two e1000e threads accessing hardware
at the same time.

description and patch updated by Jesse

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/net/e1000e/ich8lan.c b/drivers/net/e1000e/ich8lan.c
index f4b6744d71df..0b6095ba3ce9 100644
--- a/drivers/net/e1000e/ich8lan.c
+++ b/drivers/net/e1000e/ich8lan.c
@@ -380,6 +380,9 @@ static s32 e1000_get_variants_ich8lan(struct e1000_adapter *adapter)
         return 0;
 }
 
+static DEFINE_MUTEX(nvm_mutex);
+static pid_t nvm_owner = -1;
+
 /**
  *  e1000_acquire_swflag_ich8lan - Acquire software control flag
  *  @hw: pointer to the HW structure
@@ -393,6 +396,15 @@ static s32 e1000_acquire_swflag_ich8lan(struct e1000_hw *hw)
         u32 extcnf_ctrl;
         u32 timeout = PHY_CFG_TIMEOUT;
 
+        WARN_ON(preempt_count());
+
+        if (!mutex_trylock(&nvm_mutex)) {
+                WARN(1, KERN_ERR "e1000e mutex contention. Owned by pid %d\n",
+                     nvm_owner);
+                mutex_lock(&nvm_mutex);
+        }
+        nvm_owner = current->pid;
+
         while (timeout) {
                 extcnf_ctrl = er32(EXTCNF_CTRL);
                 extcnf_ctrl |= E1000_EXTCNF_CTRL_SWFLAG;
@@ -407,6 +419,8 @@ static s32 e1000_acquire_swflag_ich8lan(struct e1000_hw *hw)
 
         if (!timeout) {
                 hw_dbg(hw, "FW or HW has locked the resource for too long.\n");
+                nvm_owner = -1;
+                mutex_unlock(&nvm_mutex);
                 return -E1000_ERR_CONFIG;
         }
 
@@ -428,6 +442,9 @@ static void e1000_release_swflag_ich8lan(struct e1000_hw *hw)
         extcnf_ctrl = er32(EXTCNF_CTRL);
         extcnf_ctrl &= ~E1000_EXTCNF_CTRL_SWFLAG;
         ew32(EXTCNF_CTRL, extcnf_ctrl);
+
+        nvm_owner = -1;
+        mutex_unlock(&nvm_mutex);
 }
 
 /**