On Mon, 2016-02-15 at 16:31 +0530, Aneesh Kumar K.V wrote: > Balbir Singh <bsingharora@xxxxxxxxx> writes: > > > > Now we can't depend for mm_cpumask, a parallel find_linux_pte_hugepte > > > can happen outside that. Now i had a variant for kick_all_cpus_sync that > > > ignored idle cpus. But then that needs more verification. > > > > > > http://article.gmane.org/gmane.linux.ports.ppc.embedded/81105 > > Can be racy as a CPU moves from non-idle to idle > > > > In > > > > > + pmd_hugepage_update(vma->vm_mm, address, pmdp, ~0UL, 0); > > > + /* > > > + * This ensures that generic code that rely on IRQ disabling > > > + * to prevent a parallel THP split work as expected. > > > + */ > > > + kick_all_cpus_sync(); > > > > pmdp_invalidate()->pmd_hugepage_update() can still run in parallel with > > find_linux_pte_or_hugepte() and race.. Am I missing something? > > > > Yes. But then we make sure that the pte_t returned by > find_linux_pte_or_hugepte doesn't change to a regular pmd entry by using > that kick. Now callers of find_lnux_pte_or_hugepte will check for > _PAGE_PRESENT. So if it called before > pmd_hugepage_update(_PAGE_PRESENT), we wait for the caller to finish the > usage (via kick()). Or they bail out after finding _PAGE_PRESENT cleared. Makes sense, but I would still check the assumption about checking for _PAGE_PRESENT Balbir Singh -- 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>