On Thu, Jun 02, 2011 at 09:48:41AM -0700, Chris Wright wrote: > * Andrea Righi (andrea@xxxxxxxxxxxxxxx) wrote: > > mmh.. I can reproduce the bug also with the standard ubuntu (11.04) > > kernel. Could you post your .config? > > Andrea (Righi), can you tell me if this WARN fires? This looks > like a pure race between removing from list and checking list, i.e. > insufficient locking. Yes, it does. With this patch: [ 50.968896] WARNING: at mm/ksm.c:1305 ksm_scan_thread+0x9e3/0xe50() > > ksm_scan.mm_slot == the only registered mm > > CPU 1 (bug program) CPU 2 (ksmd) > list_empty() is false > lock > ksm_scan.mm_slot > list_del > unlock > slot == &ksm_mm_head (but list is now empty_) It seems to be the exact problem. -Andrea > > > diff --git a/mm/ksm.c b/mm/ksm.c > index 942dfc7..ab79a92 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -1301,6 +1301,7 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page) > slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); > ksm_scan.mm_slot = slot; > spin_unlock(&ksm_mmlist_lock); > + WARN_ON(slot == &ksm_mm_head); > next_mm: > ksm_scan.address = 0; > ksm_scan.rmap_list = &slot->rmap_list; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>