On Thu, Apr 11, 2013 at 06:28:31AM -0700, Greg KH wrote:
On Thu, Apr 11, 2013 at 11:55:37AM +0200, Veaceslav Falico wrote:
However, I think my patch still adds something good, cause now we have 2
cases where we basically do:
k = kset_find_obj();
if (!k)
return;
kobject_put(k);
which adds useless overhead (by using kobject_get()/kobject_put(), and
kobject_release() - which is called from kobject_put()) - where we should
only verify if there exists a kobject with the specified name.
Should I resend it with a properly fixed commit message, or it's really not
needed?
I don't think it's really needed, there is no speed/overhead issue here
and you need to do the kobject_get/put stuff anyway if you are trying to
look at a kobject.
This is the point, actually, that we don't need to look at a kobject. We
only need to know if it existed that time or not, here are those two
examples of code:
static int mod_sysfs_init(struct module *mod)
{
int err;
struct kobject *kobj;
...
kobj = kset_find_obj(module_kset, mod->name);
if (kobj) {
printk(KERN_ERR "%s: module is already loaded\n", mod->name);
kobject_put(kobj);
err = -EINVAL;
goto out;
}
...
So we just verify if there's a kobject with mod->name, and if it exists -
_put() it back and return, otherwise do nothing (with it).
Same here:
static char *make_slot_name(const char *name)
{
...
for (;;) {
struct kobject *dup_slot;
dup_slot = kset_find_obj(pci_slots_kset, new_name);
if (!dup_slot)
break;
kobject_put(dup_slot);
...
We look if there exists a kobject named new_name in pci_slots_kset, if yes
- free it and try another name, if not - then we're good to go.
In both examples we don't look at that kobject, and only uselessly
_get()/_put() it. And it looks a bit ugly. After the patch, in both cases,
it takes only one call to kset_obj_exists() to find out if the object
exists at that time.
However, I have absolutely no knowledge/experience in this domain and might
for sure be missing something. Sorry if it's the case.
thanks,
greg k-h
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