Commit 53fb95d3 authored by Matt Mackall's avatar Matt Mackall Committed by David S. Miller

[NETPOLL]: fix initialization/NAPI race

This fixes a race during initialization with the NAPI softirq
processing by using an RCU approach.

This race was discovered when refill_skbs() was added to
the setup code.
Signed-off-by: default avatarMatt Mackall <mpm@selenic.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 26520765
...@@ -9,6 +9,7 @@ ...@@ -9,6 +9,7 @@
#include <linux/netdevice.h> #include <linux/netdevice.h>
#include <linux/interrupt.h> #include <linux/interrupt.h>
#include <linux/rcupdate.h>
#include <linux/list.h> #include <linux/list.h>
struct netpoll; struct netpoll;
...@@ -61,25 +62,31 @@ static inline int netpoll_rx(struct sk_buff *skb) ...@@ -61,25 +62,31 @@ static inline int netpoll_rx(struct sk_buff *skb)
return ret; return ret;
} }
static inline void netpoll_poll_lock(struct net_device *dev) static inline void *netpoll_poll_lock(struct net_device *dev)
{ {
rcu_read_lock(); /* deal with race on ->npinfo */
if (dev->npinfo) { if (dev->npinfo) {
spin_lock(&dev->npinfo->poll_lock); spin_lock(&dev->npinfo->poll_lock);
dev->npinfo->poll_owner = smp_processor_id(); dev->npinfo->poll_owner = smp_processor_id();
return dev->npinfo;
} }
return NULL;
} }
static inline void netpoll_poll_unlock(struct net_device *dev) static inline void netpoll_poll_unlock(void *have)
{ {
if (dev->npinfo) { struct netpoll_info *npi = have;
dev->npinfo->poll_owner = -1;
spin_unlock(&dev->npinfo->poll_lock); if (npi) {
npi->poll_owner = -1;
spin_unlock(&npi->poll_lock);
} }
rcu_read_unlock();
} }
#else #else
#define netpoll_rx(a) 0 #define netpoll_rx(a) 0
#define netpoll_poll_lock(a) #define netpoll_poll_lock(a) 0
#define netpoll_poll_unlock(a) #define netpoll_poll_unlock(a)
#endif #endif
......
...@@ -1696,6 +1696,7 @@ static void net_rx_action(struct softirq_action *h) ...@@ -1696,6 +1696,7 @@ static void net_rx_action(struct softirq_action *h)
struct softnet_data *queue = &__get_cpu_var(softnet_data); struct softnet_data *queue = &__get_cpu_var(softnet_data);
unsigned long start_time = jiffies; unsigned long start_time = jiffies;
int budget = netdev_budget; int budget = netdev_budget;
void *have;
local_irq_disable(); local_irq_disable();
...@@ -1709,10 +1710,10 @@ static void net_rx_action(struct softirq_action *h) ...@@ -1709,10 +1710,10 @@ static void net_rx_action(struct softirq_action *h)
dev = list_entry(queue->poll_list.next, dev = list_entry(queue->poll_list.next,
struct net_device, poll_list); struct net_device, poll_list);
netpoll_poll_lock(dev); have = netpoll_poll_lock(dev);
if (dev->quota <= 0 || dev->poll(dev, &budget)) { if (dev->quota <= 0 || dev->poll(dev, &budget)) {
netpoll_poll_unlock(dev); netpoll_poll_unlock(have);
local_irq_disable(); local_irq_disable();
list_del(&dev->poll_list); list_del(&dev->poll_list);
list_add_tail(&dev->poll_list, &queue->poll_list); list_add_tail(&dev->poll_list, &queue->poll_list);
...@@ -1721,7 +1722,7 @@ static void net_rx_action(struct softirq_action *h) ...@@ -1721,7 +1722,7 @@ static void net_rx_action(struct softirq_action *h)
else else
dev->quota = dev->weight; dev->quota = dev->weight;
} else { } else {
netpoll_poll_unlock(dev); netpoll_poll_unlock(have);
dev_put(dev); dev_put(dev);
local_irq_disable(); local_irq_disable();
} }
......
...@@ -732,6 +732,9 @@ int netpoll_setup(struct netpoll *np) ...@@ -732,6 +732,9 @@ int netpoll_setup(struct netpoll *np)
/* last thing to do is link it to the net device structure */ /* last thing to do is link it to the net device structure */
ndev->npinfo = npinfo; ndev->npinfo = npinfo;
/* avoid racing with NAPI reading npinfo */
synchronize_rcu();
return 0; return 0;
release: release:
......
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