Re: [PATCH V4 1/3] livepatch: remove 'struct completion finish' from klp_patch
From: Petr Mladek <pmladek@suse.com>
Date: 2021-11-02 15:56:21
Also in:
lkml
On Tue 2021-11-02 22:59:30, Ming Lei wrote:
The completion finish is just for waiting release of the klp_patch object, then releases module refcnt. We can simply drop the module refcnt in the kobject release handler of klp_patch. This way also helps to support allocating klp_patch from heap.
IMHO, this is wrong assumption. kobject_put() might do everyting
asynchronously, see:
kobject_put()
kobject_release()
INIT_DELAYED_WORK(&kobj->release, kobject_delayed_cleanup);
schedule_delayed_work(&kobj->release, delay);
asynchronously:
kobject_delayed_cleanup()
kobject_cleanup()
__kobject_del()
quoted hunk ↗ jump to hunk
Signed-off-by: Ming Lei <redacted> --- include/linux/livepatch.h | 1 - kernel/livepatch/core.c | 12 +++--------- 2 files changed, 3 insertions(+), 10 deletions(-)diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 2614247a9781..9712818997c5 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h@@ -170,7 +170,6 @@ struct klp_patch { bool enabled; bool forced; struct work_struct free_work; - struct completion finish; }; #define klp_for_each_object_static(patch, obj) \diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 335d988bd811..b967b4b0071b 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c@@ -551,10 +551,10 @@ static int klp_add_nops(struct klp_patch *patch) static void klp_kobj_release_patch(struct kobject *kobj) { - struct klp_patch *patch; + struct klp_patch *patch = container_of(kobj, struct klp_patch, kobj); - patch = container_of(kobj, struct klp_patch, kobj); - complete(&patch->finish); + if (!patch->forced) + module_put(patch->mod); } static struct kobj_type klp_ktype_patch = {@@ -678,11 +678,6 @@ static void klp_free_patch_finish(struct klp_patch *patch) * cannot get enabled again. */ kobject_put(&patch->kobj); - wait_for_completion(&patch->finish); - - /* Put the module after the last access to struct klp_patch. */ - if (!patch->forced) - module_put(patch->mod);
klp_free_patch_finish() does not longer wait until the release callbacks are called. klp_free_patch_finish() is called also in klp_enable_patch() error path. klp_enable_patch() is called in module_init(). For example, see samples/livepatch/livepatch-sample.c The module must not get removed until the release callbacks are called. Does the module loader check the module reference counter when module_init() fails? Best Regards, Petr