From 4508a7a734b111b8b7e39986237d84acb1168dd0 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Mon, 20 Mar 2006 17:53:53 +1100
Subject: [PATCH] sysfs: Allow sysfs attribute files to be pollable
It works like this:
Open the file
Read all the contents.
Call poll requesting POLLERR or POLLPRI (so select/exceptfds works)
When poll returns,
close the file and go to top of loop.
or lseek to start of file and go back to the 'read'.
Events are signaled by an object manager calling
sysfs_notify(kobj, dir, attr);
If the dir is non-NULL, it is used to find a subdirectory which
contains the attribute (presumably created by sysfs_create_group).
This has a cost of one int per attribute, one wait_queuehead per kobject,
one int per open file.
The name "sysfs_notify" may be confused with the inotify
functionality. Maybe it would be nice to support inotify for sysfs
attributes as well?
This patch also uses sysfs_notify to allow /sys/block/md*/md/sync_action
to be pollable
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
lib/kobject.c | 1 +
1 file changed, 1 insertion(+)
(limited to 'lib')
diff --git a/lib/kobject.c b/lib/kobject.c
index 25204a41a9b0..01d957513940 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -128,6 +128,7 @@ void kobject_init(struct kobject * kobj)
{
kref_init(&kobj->kref);
INIT_LIST_HEAD(&kobj->entry);
+ init_waitqueue_head(&kobj->poll);
kobj->kset = kset_get(kobj->kset);
}
--
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