sysfs: move sysfs file poll implementation to sysfs_open_dirent

Sysfs file poll implementation is scattered over sysfs and kobject.
Event numbering is done in sysfs_dirent but wait itself is done on
kobject.  This not only unecessarily bloats both kobject and
sysfs_dirent but is also buggy - if a sysfs_dirent is removed while
there still are pollers, the associaton betwen the kobject and
sysfs_dirent breaks and kobject may be freed with the pollers still
sleeping on it.

This patch moves whole poll implementation into sysfs_open_dirent.
Each time a sysfs_open_dirent is created, event number restarts from 1
and pollers sleep on sysfs_open_dirent.  As event sequence number is
meaningless without any open file and pollers should have open file
and thus sysfs_open_dirent, this ephemeral event counting works and is
a saner implementation.

This patch fixes the dnagling sleepers bug and reduces the sizes of
kobject and sysfs_dirent by one pointer.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 0 insertions, 1 deletions

diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index 0777b3f57ae6..a8a84fcccbc0 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -66,7 +66,6 @@ struct kobject {
         struct kset             * kset;
         struct kobj_type        * ktype;
         struct sysfs_dirent     * sd;
-        wait_queue_head_t       poll;
 };
 
 extern int kobject_set_name(struct kobject *, const char *, ...)