This patch ties network device refcounts and module ref counts
together. It works for IPV4 and the dev->destructor problem is fixed,
at least for the Ethernet bridge device. Unregister and shutdown
work correctly, and modules can be removed when expected.
BUT: lots of dev_hold usage would need more auditing.
No idea what the performance impact is yet.
diff -urNp -X dontdiff linux-2.5/include/linux/netdevice.h
linux-2.5-dev/include/linux/netdevice.h
--- linux-2.5/include/linux/netdevice.h 2003-04-14 13:32:21.000000000 -0700
+++ linux-2.5-dev/include/linux/netdevice.h 2003-05-06 15:11:25.000000000
-0700
@@ -29,6 +29,7 @@
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <linux/kobject.h>
+#include <linux/module.h>
#include <asm/atomic.h>
#include <asm/cache.h>
@@ -629,12 +630,32 @@ extern int netdev_finish_unregister(stru
static inline void dev_put(struct net_device *dev)
{
+ module_put(dev->owner);
if (atomic_dec_and_test(&dev->refcnt))
netdev_finish_unregister(dev);
}
-#define __dev_put(dev) atomic_dec(&(dev)->refcnt)
-#define dev_hold(dev) atomic_inc(&(dev)->refcnt)
+static inline void __dev_put(struct net_device *dev)
+{
+ module_put(dev->owner);
+ atomic_dec(&dev->refcnt);
+}
+
+static inline void dev_hold(struct net_device *dev)
+{
+ __module_get(dev->owner);
+ atomic_inc(&dev->refcnt);
+}
+
+static inline int dev_try_hold(struct net_device *dev)
+{
+ int ret = 0;
+ if (try_module_get(dev->owner)){
+ atomic_inc(&dev->refcnt);
+ ret = 1;
+ }
+ return ret;
+}
/* Carrier loss detection, dial on demand. The functions netif_carrier_on
* and _off may be called from IRQ context, but it is caller
diff -urNp -X dontdiff linux-2.5/kernel/module.c linux-2.5-dev/kernel/module.c
--- linux-2.5/kernel/module.c 2003-04-30 11:19:23.000000000 -0700
+++ linux-2.5-dev/kernel/module.c 2003-05-06 13:13:20.000000000 -0700
@@ -214,6 +214,8 @@ static void module_unload_init(struct mo
INIT_LIST_HEAD(&mod->modules_which_use_me);
for (i = 0; i < NR_CPUS; i++)
atomic_set(&mod->ref[i].count, 0);
+ /* Hold reference count during initialization. */
+ atomic_set(&mod->ref[smp_processor_id()].count, 1);
/* Backwards compatibility macros put refcount during init. */
mod->waiter = current;
}
@@ -500,16 +502,6 @@ sys_delete_module(const char __user *nam
goto out;
}
- /* Coming up? Allow force on stuck modules. */
- if (mod->state == MODULE_STATE_COMING) {
- forced = try_force(flags);
- if (!forced) {
- /* This module can't be removed */
- ret = -EBUSY;
- goto out;
- }
- }
-
/* If it has an init func, it must have an exit func to unload */
if ((mod->init != init_module && mod->exit == cleanup_module)
|| mod->unsafe) {
@@ -1448,6 +1440,7 @@ sys_init_module(void __user *umod,
printk(KERN_ERR "%s: module is now stuck!\n",
mod->name);
else {
+ module_put(mod);
down(&module_mutex);
free_module(mod);
up(&module_mutex);
@@ -1463,6 +1456,9 @@ sys_init_module(void __user *umod,
mod->init_size = 0;
up(&module_mutex);
+ /* Drop initial reference. */
+ module_put(mod);
+
return 0;
}
diff -urNp -X dontdiff linux-2.5/net/core/dev.c linux-2.5-dev/net/core/dev.c
--- linux-2.5/net/core/dev.c 2003-05-05 09:41:03.000000000 -0700
+++ linux-2.5-dev/net/core/dev.c 2003-05-06 16:07:15.000000000 -0700
@@ -1,3 +1,4 @@
+#define NET_REFCNT_DEBUG 1
/*
* NET3 Protocol independent device support routines.
*
@@ -440,8 +441,8 @@ struct net_device *dev_get_by_name(const
read_lock(&dev_base_lock);
dev = __dev_get_by_name(name);
- if (dev)
- dev_hold(dev);
+ if (dev && !dev_try_hold(dev))
+ dev = NULL;
read_unlock(&dev_base_lock);
return dev;
}
@@ -513,8 +514,8 @@ struct net_device *dev_get_by_index(int
read_lock(&dev_base_lock);
dev = __dev_get_by_index(ifindex);
- if (dev)
- dev_hold(dev);
+ if (dev && !dev_try_hold(dev))
+ dev = NULL;
read_unlock(&dev_base_lock);
return dev;
}
@@ -563,8 +564,8 @@ struct net_device * dev_get_by_flags(uns
read_lock(&dev_base_lock);
dev = __dev_get_by_flags(if_flags, mask);
- if (dev)
- dev_hold(dev);
+ if (dev && !dev_try_hold(dev))
+ dev = NULL;
read_unlock(&dev_base_lock);
return dev;
}
@@ -1312,7 +1313,9 @@ int netif_rx(struct sk_buff *skb)
goto drop;
enqueue:
- dev_hold(skb->dev);
+ if (!dev_try_hold(skb->dev))
+ goto drop;
+
__skb_queue_tail(&queue->input_pkt_queue, skb);
#ifndef OFFLINE_SAMPLE
get_sample_stats(this_cpu);
@@ -1990,9 +1993,8 @@ int netdev_set_master(struct net_device
ASSERT_RTNL();
if (master) {
- if (old)
+ if (old || !dev_try_hold(master))
return -EBUSY;
- dev_hold(master);
}
br_write_lock_bh(BR_NETPROTO_LOCK);
@@ -2609,10 +2611,11 @@ int register_netdevice(struct net_device
set_bit(__LINK_STATE_PRESENT, &dev->state);
dev->next = NULL;
+ atomic_inc(&dev->refcnt);
dev_init_scheduler(dev);
write_lock_bh(&dev_base_lock);
*dp = dev;
- dev_hold(dev);
+
dev->deadbeaf = 0;
write_unlock_bh(&dev_base_lock);
@@ -2809,7 +2812,9 @@ int unregister_netdevice(struct net_devi
}
out:
kobject_unregister(&dev->kobj);
- dev_put(dev);
+
+ atomic_dec(&dev->refcnt);
+
return 0;
}
@@ -2900,7 +2905,11 @@ static int __init net_dev_init(void)
#endif
dev->xmit_lock_owner = -1;
dev->iflink = -1;
- dev_hold(dev);
+
+ if (!dev_try_hold(dev)) {
+ dev->deadbeaf = 1;
+ dp = &dev->next;
+ }
/*
* Allocate name. If the init() fails
diff -urNp -X dontdiff linux-2.5/net/ipv4/devinet.c
linux-2.5-dev/net/ipv4/devinet.c
--- linux-2.5/net/ipv4/devinet.c 2003-04-14 13:32:26.000000000 -0700
+++ linux-2.5-dev/net/ipv4/devinet.c 2003-05-06 15:16:03.000000000 -0700
@@ -559,6 +559,9 @@ int devinet_ioctl(unsigned int cmd, void
if ((dev = __dev_get_by_name(ifr.ifr_name)) == NULL)
goto done;
+ if (!dev_try_hold(dev))
+ goto done;
+
if (colon)
*colon = ':';
@@ -591,7 +594,7 @@ int devinet_ioctl(unsigned int cmd, void
ret = -EADDRNOTAVAIL;
if (!ifa && cmd != SIOCSIFADDR && cmd != SIOCSIFFLAGS)
- goto done;
+ goto put;
switch(cmd) {
case SIOCGIFADDR: /* Get interface address */
@@ -700,12 +703,15 @@ int devinet_ioctl(unsigned int cmd, void
}
break;
}
+put:
+ dev_put(dev);
done:
rtnl_unlock();
dev_probe_unlock();
out:
return ret;
rarok:
+ dev_put(dev);
rtnl_unlock();
dev_probe_unlock();
ret = copy_to_user(arg, &ifr, sizeof(struct ifreq)) ? -EFAULT : 0;
diff -urNp -X dontdiff linux-2.5/net/ipv4/fib_frontend.c
linux-2.5-dev/net/ipv4/fib_frontend.c
--- linux-2.5/net/ipv4/fib_frontend.c 2003-04-14 13:32:26.000000000 -0700
+++ linux-2.5-dev/net/ipv4/fib_frontend.c 2003-05-06 15:16:03.000000000
-0700
@@ -115,9 +115,9 @@ struct net_device * ip_dev_find(u32 addr
if (res.type != RTN_LOCAL)
goto out;
dev = FIB_RES_DEV(res);
- if (dev)
- atomic_inc(&dev->refcnt);
+ if (dev)
+ dev_hold(dev);
out:
fib_res_put(&res);
return dev;
diff -urNp -X dontdiff linux-2.5/net/ipv4/fib_semantics.c
linux-2.5-dev/net/ipv4/fib_semantics.c
--- linux-2.5/net/ipv4/fib_semantics.c 2003-04-29 09:57:41.000000000 -0700
+++ linux-2.5-dev/net/ipv4/fib_semantics.c 2003-05-06 15:10:40.000000000
-0700
@@ -406,7 +406,7 @@ static int fib_check_nh(const struct rtm
if (!(dev->flags&IFF_UP))
return -ENETDOWN;
nh->nh_dev = dev;
- atomic_inc(&dev->refcnt);
+ dev_hold(dev);
nh->nh_scope = RT_SCOPE_LINK;
return 0;
}
@@ -429,7 +429,7 @@ static int fib_check_nh(const struct rtm
nh->nh_oif = FIB_RES_OIF(res);
if ((nh->nh_dev = FIB_RES_DEV(res)) == NULL)
goto out;
- atomic_inc(&nh->nh_dev->refcnt);
+ dev_hold(nh->nh_dev);
err = -ENETDOWN;
if (!(nh->nh_dev->flags & IFF_UP))
goto out;
@@ -451,7 +451,7 @@ out:
return -ENETDOWN;
}
nh->nh_dev = in_dev->dev;
- atomic_inc(&nh->nh_dev->refcnt);
+ dev_hold(nh->nh_dev);
nh->nh_scope = RT_SCOPE_HOST;
in_dev_put(in_dev);
}
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