On 12/6/22 08:45, Peter Xu wrote:
I've got a fixup attached. John, since this got your attention please also have a look too in case there's further issues.
Well, one question: Normally, the pattern of "release_lock(A); call f(); acquire_lock(A);" is tricky, because one must revalidate that the state protected by A has not changed while the lock was released. However, in this case, it's letting page fault handling proceed, which already assumes that pages might be gone, so generally that seems OK. However, I'm lagging behind on understanding what the vma lock actually protects. It seems to be a hugetlb-specific protection for concurrent freeing of the page tables? If so, then running a page fault handler seems safe. If there's something else it protects, then we might need to revalidate that after re-acquiring the vma lock. Also, scattering hugetlb-specific locks throughout mm seems like an unfortuate thing, I wonder if there is a longer term plan to Not Do That? thanks, -- John Hubbard NVIDIA
