Ingo,
Any thoughts on the patch?
Thanks,
Mark
-----Original Message-----
From: Beauchemin, Mark
Sent: Tuesday, August 07, 2007 3:42 PM
To: 'Ingo Molnar'
Cc: Thomas Gleixner; linux-kernel@vger.kernel.org; David Miller
Subject: RE: [PATCH -rt] Preemption problem in kernel RT Patch
diff -ur linux-2.6.23-rc1-rt0/include/linux/netdevice.h linux-2.6.23-rc1-rt0_new/include/linux/netdevice.h
--- linux-2.6.23-rc1-rt0/include/linux/netdevice.h 2007-07-24 15:17:07.000000000 -0400
+++ linux-2.6.23-rc1-rt0_new/include/linux/netdevice.h 2007-08-06 09:26:51.000000000 -0400
@@ -468,7 +468,7 @@
/* cpu id of processor entered to hard_start_xmit or -1,
if nobody entered there.
*/
- int xmit_lock_owner;
+ void * xmit_lock_owner;
void *priv; /* pointer to private data */
int (*hard_start_xmit) (struct sk_buff *skb,
struct net_device *dev);
@@ -1041,32 +1041,34 @@
static inline void netif_tx_lock(struct net_device *dev)
{
spin_lock(&dev->_xmit_lock);
- dev->xmit_lock_owner = raw_smp_processor_id();
+ dev->xmit_lock_owner = (void *)current;
}
static inline void netif_tx_lock_bh(struct net_device *dev)
{
spin_lock_bh(&dev->_xmit_lock);
- dev->xmit_lock_owner = raw_smp_processor_id();
+ dev->xmit_lock_owner = (void *)current;
}
static inline int netif_tx_trylock(struct net_device *dev)
{
int ok = spin_trylock(&dev->_xmit_lock);
if (likely(ok))
- dev->xmit_lock_owner = raw_smp_processor_id();
+ {
+ dev->xmit_lock_owner = (void *)current;
+ }
return ok;
}
static inline void netif_tx_unlock(struct net_device *dev)
{
- dev->xmit_lock_owner = -1;
+ dev->xmit_lock_owner = (void *)-1;
spin_unlock(&dev->_xmit_lock);
}
static inline void netif_tx_unlock_bh(struct net_device *dev)
{
- dev->xmit_lock_owner = -1;
+ dev->xmit_lock_owner = (void *)-1;
spin_unlock_bh(&dev->_xmit_lock);
}
diff -ur linux-2.6.23-rc1-rt0/net/core/dev.c linux-2.6.23-rc1-rt0_new/net/core/dev.c
--- linux-2.6.23-rc1-rt0/net/core/dev.c 2007-07-24 15:17:07.000000000 -0400
+++ linux-2.6.23-rc1-rt0_new/net/core/dev.c 2007-08-07 15:22:31.000000000 -0400
@@ -1588,16 +1588,7 @@
Either shot noqueue qdisc, it is even simpler 8)
*/
if (dev->flags & IFF_UP) {
- /*
- * No need to check for recursion with threaded interrupts:
- */
-#ifdef CONFIG_PREEMPT_RT
- if (1) {
-#else
- int cpu = raw_smp_processor_id(); /* ok because BHs are off */
-
- if (dev->xmit_lock_owner != cpu) {
-#endif
+ if (dev->xmit_lock_owner != (void *)current) {
HARD_TX_LOCK(dev);
if (!netif_queue_stopped(dev) &&
@@ -3349,7 +3340,7 @@
spin_lock_init(&dev->queue_lock);
spin_lock_init(&dev->_xmit_lock);
netdev_set_lockdep_class(&dev->_xmit_lock, dev->type);
- dev->xmit_lock_owner = -1;
+ dev->xmit_lock_owner = (void *)-1;
spin_lock_init(&dev->ingress_lock);
dev->iflink = -1;
diff -ur linux-2.6.23-rc1-rt0/net/mac80211/ieee80211.c linux-2.6.23-rc1-rt0_new/net/mac80211/ieee80211.c
--- linux-2.6.23-rc1-rt0/net/mac80211/ieee80211.c 2007-07-24 15:15:57.000000000 -0400
+++ linux-2.6.23-rc1-rt0_new/net/mac80211/ieee80211.c 2007-08-07 15:21:28.000000000 -0400
@@ -2413,7 +2413,7 @@
static inline void netif_tx_lock_nested(struct net_device *dev, int subclass)
{
spin_lock_nested(&dev->_xmit_lock, subclass);
- dev->xmit_lock_owner = smp_processor_id();
+ dev->xmit_lock_owner = (void *)current;
}
static void ieee80211_set_multicast_list(struct net_device *dev)
diff -ur linux-2.6.23-rc1-rt0/net/sched/sch_generic.c linux-2.6.23-rc1-rt0_new/net/sched/sch_generic.c
--- linux-2.6.23-rc1-rt0/net/sched/sch_generic.c 2007-07-24 15:17:07.000000000 -0400
+++ linux-2.6.23-rc1-rt0_new/net/sched/sch_generic.c 2007-08-07 15:20:10.000000000 -0400
@@ -88,7 +88,7 @@
{
int ret;
- if (unlikely(dev->xmit_lock_owner == smp_processor_id())) {
+ if (unlikely(dev->xmit_lock_owner == (void *)current)) {
/*
* Same CPU holding the lock. It may be a transient
* configuration error, when hard_start_xmit() recurses. We
@@ -153,7 +153,13 @@
if (!lockless) {
#ifdef CONFIG_PREEMPT_RT
- netif_tx_lock(dev);
+ if (dev->xmit_lock_owner == (void *)current) {
+ kfree_skb(skb);
+ if (net_ratelimit())
+ printk(KERN_DEBUG "Dead loop on netdevice %s, fix it urgently!\n", dev->name);
+ return -1;
+ }
+ netif_tx_lock(dev);
#else
if (netif_tx_trylock(dev))
/* Another CPU grabbed the driver tx lock */
-
