Hello Satyam,
and this is why we have to use the dual-list mechanism to react to the net
device rename. This isn't so obvious, a comment at the point where you
declare modify_target_list would be nice? (BTW temporary_list would be
a better name for that, IMO)
All right, my patches are short of comments. So, I will add comments
to the ambiguous codes.
Ok, so reading through the code makes it obvious that this mutex is used
to protect against the following race:
Thread #1 Thread #2
========= =========
[ NETDEV_CHANGENAME notifier ] [ ioctl(NETCON_REMOVE_TARGET) ]
netconsole_event()
move from target_list to temp list
work on temp list
kobject_unregister()
-> release_target()
-> remove_target()
move back to target_list
Which would mean a deleted/removed target added back => *boom*
But, the race still hasn't been closed properly!
You're taking the mutex only around "work on temp list" which is
insufficient, you need to ensure atomicity inside netconsole_event()
_completely_ like this (renaming netdev_change_sem to
netdev_changename_mtx):
After the target moves from target_list to temporary_list,
the kobject_unregister() of possible raced target isn't called
in ioctl(NETCON_REMOVE_TARGET) because the target_list doesn't contain
the target .
I have the wrong idea?
+static char *make_netdev_class_name(char *netdev_name)
+{
+ char *name;
+
+ name = kasprintf(GFP_KERNEL, "net:%s", netdev_name);
Why the "net:" prefix in the filename?
Because I drew upon dev_change_name() method in net/core/dev.c.
The device_rename() in the above function makes use of same prefix
related to netdev.
static int setup_target_sysfs(struct netconsole_target *nt)
{
+ int retval = 0;
+ char *name;
+
kobject_set_name(&nt->obj, "port%d", nt->id);
nt->obj.parent = &netconsole_miscdev.this_device->kobj;
nt->obj.ktype = &target_ktype;
- return kobject_register(&nt->obj);
+ retval = kobject_register(&nt->obj);
+ name = make_netdev_class_name(nt->np.dev_name);
+ if (!name)
+ return -ENOMEM;
Just call kasprintf() directly, why the obfuscation?
I drew upon dev_change_name() method in net/core/dev.c.
Thanks
--
Keiichi KII
NEC Corporation OSS Platform Development Division
E-mail: [email protected]
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