Messages in this thread | | | Date | Wed, 7 Dec 2022 15:54:34 -0800 | Subject | Re: [PATCH v2 05/10] mm/hugetlb: Make userfaultfd_huge_must_wait() safe to pmd unshare | From | John Hubbard <> |
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On 12/7/22 15:44, Peter Xu wrote: > The part that matters in the comment is "need to be before setting current > state". > > blocking_state = userfaultfd_get_blocking_state(vmf->flags); > if (is_vm_hugetlb_page(vma)) > hugetlb_vma_lock_read(vma); > set_current_state(blocking_state); > > down_read() can sleep and also modify the task state, we cannot take the > lock after that point because otherwise the task state will be messed up. >
OK, how about:
/* * Take the vma lock now, in order to safely call * userfaultfd_huge_must_wait() a little bit later. Because acquiring * the (sleepable) vma lock potentially modifies the current task state, * that must be before explicitly calling set_current_state(). */
Other than that, the patch looks good, so:
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
thanks, -- John Hubbard NVIDIA
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