Re: [PATCH 26/41] kernel/fork: assert no VMA readers during its destruction
From: Michal Hocko <mhocko@suse.com>
Date: 2023-01-17 15:45:27
Also in:
linux-arm-kernel, linux-mm, lkml
On Mon 09-01-23 12:53:21, Suren Baghdasaryan wrote:
quoted hunk ↗ jump to hunk
Assert there are no holders of VMA lock for reading when it is about to be destroyed. Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- 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