On Tue, Sep 24, 2019 at 11:37:09AM -0700, Bart Van Assche wrote: > On 9/23/19 8:12 AM, Ming Lei wrote: > > @@ -523,11 +521,9 @@ void elv_unregister_queue(struct request_queue *q) > > kobject_uevent(&e->kobj, KOBJ_REMOVE); > > kobject_del(&e->kobj); > > - mutex_lock(&q->sysfs_lock); > > e->registered = 0; > > /* Re-enable throttling in case elevator disabled it */ > > wbt_enable_default(q); > > - mutex_unlock(&q->sysfs_lock); > > } > > } > > Does this patch cause sysfs_lock to be held around kobject_del(&e->kobj)? Yes. > Since sysfs_lock is locked from inside elv_attr_show() and elv_attr_store(), The request queue's sysfs_lock isn't required in elv_attr_show() and elv_attr_store(), and only elevator's sysfs_lock is needed in the two functions. > does this mean that this patch reintroduces the lock inversion problem that > was fixed recently? No. The lock inversion issue only existed on kobjects of q->kobj & q->mq_obj, which was fixed already given the queue's sysfs_lock is required in .show/.store callback of these two kobjects' attributes. thanks, Ming
