target/linux/mvebu/patches-4.4/042-net-mvneta-Fix-race-condition-during-stopping.patch

   1 From: Gregory CLEMENT <gregory.clement@free-electrons.com>
   2 Date: Thu, 4 Feb 2016 22:09:29 +0100
   3 Subject: [PATCH] net: mvneta: Fix race condition during stopping
   4
   5 When stopping the port, the CPU notifier are still there whereas the
   6 mvneta_stop_dev function calls mvneta_percpu_disable() on each CPUs.
   7 It was possible to have a new CPU coming at this point which could be
   8 racy.
   9
  10 This patch adds a flag preventing executing the code notifier for a new
  11 CPU when the port is stopping. It also uses the spinlock introduces
  12 previously. To avoid the deadlock, the lock has been moved outside the
  13 mvneta_percpu_elect function.
  14
  15 Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
  16 Signed-off-by: David S. Miller <davem@davemloft.net>
  17 ---
  18
  19 --- a/drivers/net/ethernet/marvell/mvneta.c
  20 +++ b/drivers/net/ethernet/marvell/mvneta.c
  21 @@ -374,6 +374,7 @@ struct mvneta_port {
  22          * ensuring that the configuration remains coherent.
  23          */
  24         spinlock_t lock;
  25 +       bool is_stopped;
  26
  27         /* Core clock */
  28         struct clk *clk;
  29 @@ -2857,16 +2858,14 @@ static void mvneta_percpu_disable(void *
  30         disable_percpu_irq(pp->dev->irq);
  31  }
  32
  33 +/* Electing a CPU must be done in an atomic way: it should be done
  34 + * after or before the removal/insertion of a CPU and this function is
  35 + * not reentrant.
  36 + */
  37  static void mvneta_percpu_elect(struct mvneta_port *pp)
  38  {
  39         int elected_cpu = 0, max_cpu, cpu, i = 0;
  40
  41 -       /* Electing a CPU must be done in an atomic way: it should be
  42 -        * done after or before the removal/insertion of a CPU and
  43 -        * this function is not reentrant.
  44 -        */
  45 -       spin_lock(&pp->lock);
  46 -
  47         /* Use the cpu associated to the rxq when it is online, in all
  48          * the other cases, use the cpu 0 which can't be offline.
  49          */
  50 @@ -2910,7 +2909,6 @@ static void mvneta_percpu_elect(struct m
  51                 i++;
  52
  53         }
  54 -       spin_unlock(&pp->lock);
  55  };
  56
  57  static int mvneta_percpu_notifier(struct notifier_block *nfb,
  58 @@ -2924,6 +2922,14 @@ static int mvneta_percpu_notifier(struct
  59         switch (action) {
  60         case CPU_ONLINE:
  61         case CPU_ONLINE_FROZEN:
  62 +               spin_lock(&pp->lock);
  63 +               /* Configuring the driver for a new CPU while the
  64 +                * driver is stopping is racy, so just avoid it.
  65 +                */
  66 +               if (pp->is_stopped) {
  67 +                       spin_unlock(&pp->lock);
  68 +                       break;
  69 +               }
  70                 netif_tx_stop_all_queues(pp->dev);
  71
  72                 /* We have to synchronise on tha napi of each CPU
  73 @@ -2961,6 +2967,7 @@ static int mvneta_percpu_notifier(struct
  74                         MVNETA_CAUSE_LINK_CHANGE |
  75                         MVNETA_CAUSE_PSC_SYNC_CHANGE);
  76                 netif_tx_start_all_queues(pp->dev);
  77 +               spin_unlock(&pp->lock);
  78                 break;
  79         case CPU_DOWN_PREPARE:
  80         case CPU_DOWN_PREPARE_FROZEN:
  81 @@ -2985,7 +2992,9 @@ static int mvneta_percpu_notifier(struct
  82         case CPU_DEAD:
  83         case CPU_DEAD_FROZEN:
  84                 /* Check if a new CPU must be elected now this on is down */
  85 +               spin_lock(&pp->lock);
  86                 mvneta_percpu_elect(pp);
  87 +               spin_unlock(&pp->lock);
  88                 /* Unmask all ethernet port interrupts */
  89                 on_each_cpu(mvneta_percpu_unmask_interrupt, pp, true);
  90                 mvreg_write(pp, MVNETA_INTR_MISC_MASK,
  91 @@ -3037,7 +3046,7 @@ static int mvneta_open(struct net_device
  92          */
  93         on_each_cpu(mvneta_percpu_enable, pp, true);
  94
  95 -
  96 +       pp->is_stopped = false;
  97         /* Register a CPU notifier to handle the case where our CPU
  98          * might be taken offline.
  99          */
 100 @@ -3070,9 +3079,18 @@ static int mvneta_stop(struct net_device
 101  {
 102         struct mvneta_port *pp = netdev_priv(dev);
 103
 104 +       /* Inform that we are stopping so we don't want to setup the
 105 +        * driver for new CPUs in the notifiers
 106 +        */
 107 +       spin_lock(&pp->lock);
 108 +       pp->is_stopped = true;
 109         mvneta_stop_dev(pp);
 110         mvneta_mdio_remove(pp);
 111         unregister_cpu_notifier(&pp->cpu_notifier);
 112 +       /* Now that the notifier are unregistered, we can release le
 113 +        * lock
 114 +        */
 115 +       spin_unlock(&pp->lock);
 116         on_each_cpu(mvneta_percpu_disable, pp, true);
 117         free_percpu_irq(dev->irq, pp->ports);
 118         mvneta_cleanup_rxqs(pp);
 119 @@ -3343,7 +3361,9 @@ static int  mvneta_config_rss(struct mvn
 120         mvreg_write(pp, MVNETA_PORT_CONFIG, val);
 121
 122         /* Update the elected CPU matching the new rxq_def */
 123 +       spin_lock(&pp->lock);
 124         mvneta_percpu_elect(pp);
 125 +       spin_unlock(&pp->lock);
 126
 127         /* We have to synchronise on the napi of each CPU */
 128         for_each_online_cpu(cpu) {