Alan Stern wrote:
> On Thu, 3 May 2007, Tejun Heo wrote:
>
>> Hello, Alan Stern.
>>
>> Alan Stern wrote:
>>>> The endpoint directory shown in the oops report does not exist if I'm not
>>>> thrashing the box with
>>>> winecfg. On Tejun Heo's suggestion, I put some debug code at the beginning
>>>> of sysfs_release() to
>>>> print a stack-dump and the kobject's path if the attr->owner field
>>>> contains 0x6b6b6b6b or
>>>> 0x5a5a5a5a poison:
>>>>
>>>> XXX debug trap owner=6b6b6b6b, path=/class/usb_endpoint/usbdev1.3_ep84
>>>> XXX debug stack-dump
>>>> [<c018462a>] sysfs_release+0x70/0xa5
>>>> [<c0151837>] __fput+0x96/0x13c
>>>> [<c014f358>] filp_close+0x51/0x58
>>>> [<c0150351>] sys_close+0x70/0xa7
>>>> [<c0102bde>] sysenter_past_esp+0x5f/0x85
>>>> [<c0270033>] unix_create1+0xa2/0xee
>>>> =======================
>>> This clearly indicates that something has been deallocated too early (or
>>> equivalently, used too late).
>> What has been filled with the 6b pattern here is struct attribute not
>> some sysfs internal object.
>
> Are you sure?
That's what the debug code seems to tell us.
static int sysfs_release(struct inode * inode, struct file * filp)
{
struct kobject * kobj = to_kobj(filp->f_path.dentry->d_parent);
struct attribute * attr = to_attr(filp->f_path.dentry);
struct module * owner = attr->owner;
struct sysfs_buffer * buffer = filp->private_data;
if ((unsigned long)owner >> 16 == 0x5a5a ||
(unsigned long)owner >> 16 == 0x6b6b) {
if (kobj != NULL) {
char *path = kobject_get_path(kobj, GFP_KERNEL);
printk("XXX debug trap owner=%p, path=%s\n", owner,
path);
kfree(path);
}
printk("XXX debug stack-dump\n");
dump_stack();
}
/* blah blah....*/
}
>> Does USB allocate struct attribute
>> dynamically for any of its attributes?
>
> No; it uses sysfs_create_group() with a static attribute group list. I
> don't know why it doesn't call device_add_group() -- maybe it was written
> before that function existed.
>
> You can see the code in drivers/usb/core/endpoint.c:usb_create_ep_files().
I see. They're static alright. That leaves us with sd pointing to
the wrong attr. I'll take a look whether that's possible.
--
tejun
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