From: Michal Schmidt <mschmidt@redhat.com>
Date: Fri, 3 Sep 2010 16:43:23 -0400
Subject: [net] bnx2x: protect a SM state change
Message-id: <20100903164323.25415.38813.stgit@brian.englab.brq.redhat.com>
Patchwork-id: 28102
O-Subject: [RHEL5.6 BZ572012 PATCH 27/46] bnx2x: Protect a SM state change
Bugzilla: 572012
RH-Acked-by: David S. Miller <davem@redhat.com>
RH-Acked-by: Stanislaw Gruszka <sgruszka@redhat.com>

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>
(cherry picked from commit a13773a53faa28cf79982601b6fc9ddb0ca45f36)

Conflicts:

	drivers/net/bnx2x.h

diff --git a/drivers/net/bnx2x.h b/drivers/net/bnx2x.h
index 3743b71..71f7e35 100644
--- a/drivers/net/bnx2x.h
+++ b/drivers/net/bnx2x.h
@@ -1067,6 +1067,9 @@ struct bnx2x {
 	int			stats_state;
 	struct net_device_stats net_stats;
 
+	/* 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;
diff --git a/drivers/net/bnx2x_main.c b/drivers/net/bnx2x_main.c
index a87e0bf..bc00d84 100644
--- a/drivers/net/bnx2x_main.c
+++ b/drivers/net/bnx2x_main.c
@@ -4848,16 +4848,18 @@ 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",
@@ -9925,6 +9927,7 @@ 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