On Thu, 2012-07-26 at 22:31 +0200, Peter Zijlstra wrote: > __do_huge_pmd_anonymous_page() contains: > > /* > * The spinlocking to take the lru_lock inside > * page_add_new_anon_rmap() acts as a full memory > * barrier to be sure clear_huge_page writes become > * visible after the set_pmd_at() write. > */ > page_add_new_anon_rmap(page, vma, haddr); > > > page_add_new_anon_rmap() doesn't look to actually do a LOCK+UNLOCK > except for unevictable pages. > > But even if it did do an unconditional LOCK+UNLOCK that doesn't make a > full memory barrier, see Documentation/memory-barriers.txt. > > In particular: > > *A = a; > LOCK > UNLOCK > *B = b; > > may occur as: > > LOCK, STORE *B, STORE *A, UNLOCK >
Also, what is that barrier() in handle_mm_fault() doing? And why doesn't it have a comment explaining that? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
