[PATCH net 1/3] net: mvneta: Fix spinlock usage

Gregory CLEMENT
2016-03-08T12:58:20Z

In the previous patch, the spinlock was not initialized. While it didn't
cause any trouble yet it could be a problem to use it uninitialized.

The most annoying part was the critical section protected by the spinlock
in mvneta_stop(). Some of the functions could sleep as pointed when
activated CONFIG_DEBUG_ATOMIC_SLEEP. Actually, in mvneta_stop() we only
need to protect the is_stopped flagged, indeed the code of the notifier
for CPU online is protected by the same spinlock, so when we get the
lock, the notifer work is done.

Reported-by: Patrick Uiterwijk <patrick@puiterwijk.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
---
drivers/net/ethernet/marvell/mvneta.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index b0ae69f84493..8dc7df2edff6 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -3070,17 +3070,17 @@ 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
+ * driver for new CPUs in the notifiers. The code of the
+ * notifier for CPU online is protected by the same spinlock,
+ * so when we get the lock, the notifer work is done.
*/
spin_lock(&pp->lock);
pp->is_stopped = true;
+ spin_unlock(&pp->lock);
+
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);
@@ -3612,6 +3612,7 @@ static int mvneta_probe(struct platform_device *pdev)
dev->ethtool_ops = &mvneta_eth_tool_ops;

pp = netdev_priv(dev);
+ spin_lock_init(&pp->lock);
pp->phy_node = phy_node;
pp->phy_interface = phy_mode;

--
2.5.0