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From: Gregory CLEMENT <gregory.clement@free-electrons.com>
Date: Thu, 4 Feb 2016 22:09:29 +0100
Subject: [PATCH] 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>
---
--- 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;
@@ -2853,16 +2854,14 @@ static void mvneta_percpu_disable(void *
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.
*/
@@ -2906,7 +2905,6 @@ static void mvneta_percpu_elect(struct m
i++;
}
- spin_unlock(&pp->lock);
};
static int mvneta_percpu_notifier(struct notifier_block *nfb,
@@ -2920,6 +2918,14 @@ static int mvneta_percpu_notifier(struct
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
@@ -2957,6 +2963,7 @@ static int mvneta_percpu_notifier(struct
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:
@@ -2981,7 +2988,9 @@ static int mvneta_percpu_notifier(struct
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,
@@ -3033,7 +3042,7 @@ static int mvneta_open(struct net_device
*/
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.
*/
@@ -3066,9 +3075,18 @@ static int mvneta_stop(struct net_device
{
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);
@@ -3339,7 +3357,9 @@ static int mvneta_config_rss(struct mvn
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) {
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