Re: [PATCH bpf-next v4] bpf: fix lockdep warning triggered by stack_map_get_build_id_offset()

[Yonghong Song <yhs@xxxxxx>]

On 9/9/21 6:33 AM, Matthew Wilcox wrote:
> On Wed, Sep 08, 2021 at 11:02:45PM -0700, Yonghong Song wrote:
> > @@ -204,9 +204,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
> >   	}
> >   
> >   	if (!work) {
> > -		mmap_read_unlock_non_owner(current->mm);
> > +		mmap_read_unlock(current->mm);
> >   	} else {
> >   		work->mm = current->mm;
> > +		rwsem_release(&current->mm->mmap_lock.dep_map, _RET_IP_);
> >   		irq_work_queue(&work->irq_work);
>
> This needs a comment before the rwsem_release().  Something like:
>
> 		/*
> 		 * The lock will be released once we're out of interrupt
> 		 * context.  Tell lockdep that we've released it now so
> 		 * it doesn't complain that we forgot to release it.
> 		 */

Thanks! Will add it in the next revision.