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SubjectPATCH: missing unlock in ipconfig - and question: appletalk delays

Hi,
I compiled a new (2.4.13) kernel for my notebook which included
appletalk support (just in case...) and found that I started getting
lots of processes hanging in 'D' state.

They were trying to down(&rtnl_sem);

I did an audit of rtnl_sem usage and found an obscure case where an
unlock was missing:

--- ./net/ipv4/ipconfig.c 2001/11/01 01:51:16 1.1
+++ ./net/ipv4/ipconfig.c 2001/11/01 02:42:26
@@ -194,8 +194,10 @@
printk(KERN_ERR "IP-Config: Failed to open %s\n", dev->name);
continue;
}
- if (!(d = kmalloc(sizeof(struct ic_device), GFP_KERNEL)))
+ if (!(d = kmalloc(sizeof(struct ic_device), GFP_KERNEL))) {
+ rtnl_shunlock();
return -1;
+ }
d->dev = dev;
*last = d;
last = &d->next;

But that wasn't the problem. The problem was that atalkd was doing
atif_probe_device under some sock_ioctl/atalk_ioctl/atif_ioctl and it
was taking a long time, and holding the rtnl_sem semaphore the whole
time.
The code suggests what it could try for some multiple of 253
seconds, which is several minutes. During this time such simple
commands as "netstat -i" wont work.

It's probably OK for it to take a long time probing the network, but
it is really fair that it hold the semaphore for the whole time??

Fortunately it does interruptible waits so I can just kill atalkd (or
maybe even not run it).

NeilBrown
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