On Mon 09-01-23 12:53:21, Suren Baghdasaryan wrote:
> Assert there are no holders of VMA lock for reading when it is about to be
> destroyed.
>
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> ---
> include/linux/mm.h | 8 ++++++++
> kernel/fork.c | 2 ++
> 2 files changed, 10 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 594e835bad9c..c464fc8a514c 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -680,6 +680,13 @@ static inline void vma_assert_write_locked(struct vm_area_struct *vma)
> VM_BUG_ON_VMA(vma->vm_lock_seq != READ_ONCE(vma->vm_mm->mm_lock_seq), vma);
> }
>
> +static inline void vma_assert_no_reader(struct vm_area_struct *vma)
> +{
> + VM_BUG_ON_VMA(rwsem_is_locked(&vma->lock) &&
> + vma->vm_lock_seq != READ_ONCE(vma->vm_mm->mm_lock_seq),
> + vma);
Do we really need to check for vm_lock_seq? rwsem_is_locked should tell
us something is wrong on its own, no? This could be somebody racing with
the vma destruction and using the write lock. Unlikely but I do not see
why to narrow debugging scope.
--
Michal Hocko
SUSE Labs
