> Hm yeah, this will fix the problem. But is there anyway we can do this
> without a lock at all? I think we wouldn't need the lock, if we didn't
> test the refcount for > 0, right? Pat, that just keeps us from getting
> a reference count on a kobject that hasn't been initialized, right?
> That is a good idea to do, but is it really necessary?
Well, it also prevents us from getting a reference to an object that is
being deleted. The chance of that happening is slim, and it indicates a
need for synchronization at a higher level (if the kobject_get() on the
object being deleted was to be delayed for some reason, they would likely
be referencing freed memory anyway).
And, in theory, an uninitialized object shouldn't be accessible, and any
code doing that is buggy, and will have other problems.
In short, I think we can remove the locks entirely. We can at least see
what happens..
-pat
===== lib/kobject.c 1.19 vs edited =====
--- 1.19/lib/kobject.c Sat Apr 12 16:20:38 2003
+++ edited/lib/kobject.c Wed Apr 16 09:57:15 2003
@@ -9,8 +9,6 @@
#include <linux/module.h>
#include <linux/stat.h>
-static spinlock_t kobj_lock = SPIN_LOCK_UNLOCKED;
-
/**
* populate_dir - populate directory with attributes.
* @kobj: object we're working on.
@@ -336,12 +334,10 @@
struct kobject * kobject_get(struct kobject * kobj)
{
struct kobject * ret = kobj;
- spin_lock(&kobj_lock);
- if (kobj && atomic_read(&kobj->refcount) > 0)
+ if (kobj)
atomic_inc(&kobj->refcount);
else
ret = NULL;
- spin_unlock(&kobj_lock);
return ret;
}
@@ -371,10 +367,8 @@
void kobject_put(struct kobject * kobj)
{
- if (!atomic_dec_and_lock(&kobj->refcount, &kobj_lock))
- return;
- spin_unlock(&kobj_lock);
- kobject_cleanup(kobj);
+ if (atomic_dec_and_test(&kobj->refcount))
+ kobject_cleanup(kobj);
}
-
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This archive was generated by hypermail 2b29 : Wed Apr 23 2003 - 22:00:19 EST