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>

diff --git a/drivers/net/e1000e/ich8lan.c b/drivers/net/e1000e/ich8lan.c
index f4b6744d71df94744849569bd60265e0ba9c5df8..0b6095ba3ce9f830b0462bb11edefca863463d0e 100644 (file)
--- 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);
 }
 
 /**