bnx2x: Protect a SM state change

Bug fix: Protect the statistics state machine state update with a
spinlock.  Otherwise there was a race condition that would cause the
statistics to stay enabled despite the fact that they were disabled in
the LINK_DOWN event handler.

Signed-off-by: Vladislav Zolotarov <vladz@broadcom.com>
Signed-off-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bnx2x.h

@@ -1062,6 +1062,10 @@ struct bnx2x {
 
 	/* used to synchronize stats collecting */
 	int			stats_state;
+
+	/* used for synchronization of concurrent threads statistics handling */
+	spinlock_t		stats_lock;
+
 	/* used by dmae command loader */
 	struct dmae_command	stats_dmae;
 	int			executer_idx;

drivers/net/bnx2x_main.c

@@ -4849,16 +4849,18 @@ static const struct {
 
 static void bnx2x_stats_handle(struct bnx2x *bp, enum bnx2x_stats_event event)
 {
-	enum bnx2x_stats_state state = bp->stats_state;
+	enum bnx2x_stats_state state;
 
 	if (unlikely(bp->panic))
 		return;
 
-	bnx2x_stats_stm[state][event].action(bp);
+	/* Protect a state change flow */
+	spin_lock_bh(&bp->stats_lock);
+	state = bp->stats_state;
 	bp->stats_state = bnx2x_stats_stm[state][event].next_state;
+	spin_unlock_bh(&bp->stats_lock);
 
-	/* Make sure the state has been "changed" */
-	smp_wmb();
+	bnx2x_stats_stm[state][event].action(bp);
 
 	if ((event != STATS_EVENT_UPDATE) || netif_msg_timer(bp))
 		DP(BNX2X_MSG_STATS, "state %d -> event %d -> state %d\n",
@@ -9908,6 +9910,7 @@ static int __devinit bnx2x_init_bp(struct bnx2x *bp)
 
 	mutex_init(&bp->port.phy_mutex);
 	mutex_init(&bp->fw_mb_mutex);
+	spin_lock_init(&bp->stats_lock);
 #ifdef BCM_CNIC
 	mutex_init(&bp->cnic_mutex);
 #endif