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SubjectRe: kernel BUG at fs/sysfs/dir.c:20!
On Thu, Nov 04, 2004 at 12:52:38PM -0800, Greg KH wrote:
> Hi,
>
> I get the following BUG in the sysfs code when I do:
> - plug in a usb-serial device.
> - open the port with 'cat /dev/ttyUSB0'
> - unplug the device.
> - stop the 'cat' process with control-C
>
> This used to work just fine before your big sysfs changes.
>
> Anything I should look at testing?
>

Hi Greg,

I was about to talk to you. There is a similar problem reported by
s390 people where we see parent kobject (directory) going away before
child kobject (sub-directory). It seems kobject code is able to handle
this, but not the sysfs. What could be happening that in sysfs_remove_dir()
of parent directory, we try to remove its contents. It works well with
the regular files as it is the final removal for sysfs_dirent corresponding
to the files. But in case of sub-directory we are doing an extra sysfs_put().
Once while removing parent and the other one being the one from when
sysfs_remove_dir() is called for the child.

The following patch worked for the s390 people, I hope same will work in
this case also.


o Do not remove sysfs_dirents corresponding to the sub-directory in
sysfs_remove_dir(). They will be removed in the sysfs_remove_dir() call
for the specific sub-directory.

Signed-off-by: <maneesh@in.ibm.com>
---

linux-2.6.10-rc1-bk14-maneesh/fs/sysfs/dir.c | 2 +-
1 files changed, 1 insertion(+), 1 deletion(-)

diff -puN fs/sysfs/dir.c~parent-before-child-removal-fix fs/sysfs/dir.c
--- linux-2.6.10-rc1-bk14/fs/sysfs/dir.c~parent-before-child-removal-fix 2004-11-04 13:37:32.000000000 -0800
+++ linux-2.6.10-rc1-bk14-maneesh/fs/sysfs/dir.c 2004-11-04 13:37:32.000000000 -0800
@@ -277,7 +277,7 @@ void sysfs_remove_dir(struct kobject * k
pr_debug("sysfs %s: removing dir\n",dentry->d_name.name);
down(&dentry->d_inode->i_sem);
list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
- if (!sd->s_element)
+ if (!sd->s_element || !(sd->s_type & SYSFS_NOT_PINNED))
continue;
list_del_init(&sd->s_sibling);
sysfs_drop_dentry(sd, dentry);
_


--
Maneesh Soni
Linux Technology Center,
IBM Austin
email: maneesh@in.ibm.com
Phone: 1-512-838-1896 Fax:
T/L : 6781896
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