Hello,
On Fri, Jul 26, 2013 at 05:59:00PM +0800, Dennis Chen wrote:
> On 07/26/2013 05:49 PM, Dennis Chen wrote:
>
> >The patch is trying its best to avoid creating a dir under a parent dir
> >which is removing from
> >the system:
> > PATH0 (create a dir under 'PARENT/...') PATH1 (remove the
> > 'PARENT/...')
> > sysfs_create_dir() { sysfs_remove_dir() {
> > ... ...
> > if (kobj->parent)
> > spin_lock(&sysfs_assoc_lock);
> > parent_sd = kobj->parent->sd; <----- kobj->sd = NULL;
> > else
> > spin_unlock(&sysfs_assoc_lock);
> > parent_sd = &sysfs_root;
> >Suppose PATH1 enter the critical section first, then PATH0 begin to execute
> >before kobj->sd
> >has been reset to NULL, possibly PATH0 will get a non-NULL parent_sd since
> >lack of the
> >sysfs_assoc_lock protection in PATH0. In this case, PATH0 think it has a
> >valid parent_sd which
> >can be freed by PATH1 in the followed, refer to the comments in the patch.
> >Maybe we need
> >to figure out a perfect solution to solve the race condition, although the
> >codes in question are
> >in slow path...
I don't think sysfs is supposed to handle multiple actors trying to
populate and destroy the directory at the same time at all, so this
seems kinda moot. Do you have a case where this actually matters?
Thanks.
--
tejun
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