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. -aneesh -- 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