net: mvneta: Fix race condition during stopping

When stopping the port, the CPU notifier are still there whereas the
mvneta_stop_dev function calls mvneta_percpu_disable() on each CPUs.
It was possible to have a new CPU coming at this point which could be
racy.

This patch adds a flag preventing executing the code notifier for a new
CPU when the port is stopping. It also uses the spinlock introduces
previously. To avoid the deadlock, the lock has been moved outside the
mvneta_percpu_elect function.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index b12a745a0e4c85b28dbe26e568d3fac492ed12c9..b0ae69f8449369585dfa82de3243f401f8a1022a 100644 (file)
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -374,6 +374,7 @@ struct mvneta_port {
         * ensuring that the configuration remains coherent.
         */
        spinlock_t lock;
+       bool is_stopped;
 
        /* Core clock */
        struct clk *clk;
@@ -2855,16 +2856,14 @@ static void mvneta_percpu_disable(void *arg)
        disable_percpu_irq(pp->dev->irq);
 }
 
+/* Electing a CPU must be done in an atomic way: it should be done
+ * after or before the removal/insertion of a CPU and this function is
+ * not reentrant.
+ */
 static void mvneta_percpu_elect(struct mvneta_port *pp)
 {
        int elected_cpu = 0, max_cpu, cpu, i = 0;
 
-       /* Electing a CPU must be done in an atomic way: it should be
-        * done after or before the removal/insertion of a CPU and
-        * this function is not reentrant.
-        */
-       spin_lock(&pp->lock);
-
        /* Use the cpu associated to the rxq when it is online, in all
         * the other cases, use the cpu 0 which can't be offline.
         */
@@ -2908,7 +2907,6 @@ static void mvneta_percpu_elect(struct mvneta_port *pp)
                i++;
 
        }
-       spin_unlock(&pp->lock);
 };
 
 static int mvneta_percpu_notifier(struct notifier_block *nfb,
@@ -2922,6 +2920,14 @@ static int mvneta_percpu_notifier(struct notifier_block *nfb,
        switch (action) {
        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
+               spin_lock(&pp->lock);
+               /* Configuring the driver for a new CPU while the
+                * driver is stopping is racy, so just avoid it.
+                */
+               if (pp->is_stopped) {
+                       spin_unlock(&pp->lock);
+                       break;
+               }
                netif_tx_stop_all_queues(pp->dev);
 
                /* We have to synchronise on tha napi of each CPU
@@ -2959,6 +2965,7 @@ static int mvneta_percpu_notifier(struct notifier_block *nfb,
                        MVNETA_CAUSE_LINK_CHANGE |
                        MVNETA_CAUSE_PSC_SYNC_CHANGE);
                netif_tx_start_all_queues(pp->dev);
+               spin_unlock(&pp->lock);
                break;
        case CPU_DOWN_PREPARE:
        case CPU_DOWN_PREPARE_FROZEN:
@@ -2983,7 +2990,9 @@ static int mvneta_percpu_notifier(struct notifier_block *nfb,
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                /* Check if a new CPU must be elected now this on is down */
+               spin_lock(&pp->lock);
                mvneta_percpu_elect(pp);
+               spin_unlock(&pp->lock);
                /* Unmask all ethernet port interrupts */
                on_each_cpu(mvneta_percpu_unmask_interrupt, pp, true);
                mvreg_write(pp, MVNETA_INTR_MISC_MASK,
@@ -3027,7 +3036,7 @@ static int mvneta_open(struct net_device *dev)
         */
        on_each_cpu(mvneta_percpu_enable, pp, true);
 
-
+       pp->is_stopped = false;
        /* Register a CPU notifier to handle the case where our CPU
         * might be taken offline.
         */
@@ -3060,9 +3069,18 @@ static int mvneta_stop(struct net_device *dev)
 {
        struct mvneta_port *pp = netdev_priv(dev);
 
+       /* Inform that we are stopping so we don't want to setup the
+        * driver for new CPUs in the notifiers
+        */
+       spin_lock(&pp->lock);
+       pp->is_stopped = true;
        mvneta_stop_dev(pp);
        mvneta_mdio_remove(pp);
        unregister_cpu_notifier(&pp->cpu_notifier);
+       /* Now that the notifier are unregistered, we can release le
+        * lock
+        */
+       spin_unlock(&pp->lock);
        on_each_cpu(mvneta_percpu_disable, pp, true);
        free_percpu_irq(dev->irq, pp->ports);
        mvneta_cleanup_rxqs(pp);
@@ -3333,7 +3351,9 @@ static int  mvneta_config_rss(struct mvneta_port *pp)
        mvreg_write(pp, MVNETA_PORT_CONFIG, val);
 
        /* Update the elected CPU matching the new rxq_def */
+       spin_lock(&pp->lock);
        mvneta_percpu_elect(pp);
+       spin_unlock(&pp->lock);
 
        /* We have to synchronise on the napi of each CPU */
        for_each_online_cpu(cpu) {