On Fri, 6 Dec 2013, Rik van Riel wrote: > > When you start migrating a page a special page migration entry is > > created that will trap all accesses to the page. You can safely flush when > > the migration entry is there. Only allow a new PTE/PMD to be put there > > *after* the tlb flush. > > A PROT_NONE or NUMA pte is just as effective as a migration pte. > The only problem is, the TLB flush was not always done... Ok then what are you trying to fix? > > Dont do that. We have migration entries for a reason. > > We do not have migration entries for hugepages, do we? Dunno. > > > > Should cause a page fault which should put the process to sleep. Process > > will safely read the page after the migration entry is removed. > > > >> flush TLB > > > > Establish the new PTE/PMD after the flush removing the migration pte > > entry and thereby avoiding the race. > > That is what this patch does. If that is the case then this patch would not be needed and the tracking of state in the mm_struct would not be necessary. -- 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>