On 2016/6/17 23:39, Mike Kravetz wrote: > On 06/17/2016 05:25 AM, Kirill A. Shutemov wrote: >> From fd22922e7b4664e83653a84331f0a95b985bff0c Mon Sep 17 00:00:00 2001 >> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> >> Date: Fri, 17 Jun 2016 15:07:03 +0300 >> Subject: [PATCH] hugetlb: fix nr_pmds accounting with shared page tables >> >> We account HugeTLB's shared page table to all processes who share it. >> The accounting happens during huge_pmd_share(). >> >> If somebody populates pud entry under us, we should decrease pagetable's >> refcount and decrease nr_pmds of the process. >> >> By mistake, I increase nr_pmds again in this case. :-/ >> It will lead to "BUG: non-zero nr_pmds on freeing mm: 2" on process' >> exit. >> >> Let's fix this by increasing nr_pmds only when we're sure that the page >> table will be used. >> >> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Nice, > Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > > I agree that we do not necessarily need a back port. I have not seen > reports of people experiencing this race and seeing the BUG (on mm > tear-down). > > zhongjiang, did someone actually hit the BUG? Or, did you find it by > code examination? > just code examination. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>