Messages in this thread | | | Date | Wed, 5 Dec 2018 14:02:20 -0500 | From | Joe Lawrence <> | Subject | Re: [PATCH v14 03/11] livepatch: Consolidate klp_free functions |
| |
On Thu, Nov 29, 2018 at 10:44:23AM +0100, Petr Mladek wrote: > The code for freeing livepatch structures is a bit scattered and tricky: > > + direct calls to klp_free_*_limited() and kobject_put() are > used to release partially initialized objects > > + klp_free_patch() removes the patch from the public list > and releases all objects except for patch->kobj > > + object_put(&patch->kobj) and the related wait_for_completion() > are called directly outside klp_mutex; this code is duplicated; > > Now, we are going to remove the registration stage to simplify the API > and the code. This would require handling more situations in > klp_enable_patch() error paths. > > More importantly, we are going to add a feature called atomic replace. > It will need to dynamically create func and object structures. We will > want to reuse the existing init() and free() functions. This would > create even more error path scenarios. > > [*] We need our own flag. Note that kobject_put() cannot be called safely > when kobj.state_initialized is set. This flag is true when kobject_add() > part failed. And it is never cleared. > [*] We need our own flag. Note that kobject_put() cannot be called safely > when kobj.state_initialized is set. This flag is true when kobject_add() > part failed. And it is never cleared. > This patch implements a more clever free functions: ^^^^^^^^^^^^^ re-wording suggestions: "simpler", "clearer", "more straightforward"
> > + checks kobj_alive flag instead of @limit[*] > > + initializes patch->list early so that the check for empty list > always works > > + The action(s) that has to be done outside klp_mutex are done > in separate klp_free_patch_finish() function. It waits only > when patch->kobj was really released via the _start() part. > > The patch does not change the existing behavior. > > [*] We need our own flag. Note that kobject_put() cannot be called safely > when kobj.state_initialized is set. This flag is true when kobject_add() > part failed. And it is never cleared.
Isn't kobj.state_initialized also true in the ordinary kobject_put() case where kobject_add() succeeded?
If so, this note could be modified slightly:
(minimal change)
[*] We need our own flag. Note that kobject_put() cannot be called safely just because kobj.state_initialized is set. This flag is even true when kobject_add() part failed. And it is never cleared.
-- or --
(rewording)
[*] We need our own flag to track that the kobject was successfully added to the hierarchy. Note that kobj.state_initialized only indicates that kobject has been initialized, not whether is has been added (and needs to be removed on cleanup).
> > Signed-off-by: Petr Mladek <pmladek@suse.com> > Cc: Josh Poimboeuf <jpoimboe@redhat.com> > Cc: Miroslav Benes <mbenes@suse.cz> > Cc: Jessica Yu <jeyu@kernel.org> > Cc: Jiri Kosina <jikos@kernel.org> > Cc: Jason Baron <jbaron@akamai.com> > ---
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
> > [ ... snip ... ] > > +static int klp_init_patch(struct klp_patch *patch) > +{ > + struct klp_object *obj; > + int ret; > + > + mutex_lock(&klp_mutex); > + > + ret = klp_init_patch_before_free(patch); > if (ret) { > mutex_unlock(&klp_mutex); > return ret; > } >
I believe klp_init_patch_before_free() accumulates more responsibilities later in the patchset, but I'll ask here: does it really need the klp_mutex since it looks to be operating only on the klp_patch, its objects and functions?
-- Joe
| |