[PATCH net 1/3] net: mvneta: Fix spinlock usage
From: Jisheng Zhang <hidden>
Date: 2016-03-09 06:47:37
Also in:
lkml, netdev
Dear Gregory, On Tue, 8 Mar 2016 13:57:04 +0100 Gregory CLEMENT wrote:
quoted hunk ↗ jump to hunk
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 <redacted> Signed-off-by: Gregory CLEMENT <redacted> --- 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);
This fix sleep in atomic issue. But
I see race here. Let's assume is_stopped is false.
cpu0: cpu1:
mvneta_percpu_notifier(): mvneta_stop():
if (pp->is_stopped) {
spin_unlock(&pp->lock);
break;
}
pp->is_stopped = true;
spin_unlock(&pp->lock);
netif_tx_stop_all_queues(pp->dev);
for_each_online_cpu(other_cpu) {
....
Thanks,
Jisheng
quoted hunk ↗ jump to hunk
+ 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;