On Wed, May 05, 2010 at 11:02:25AM -0700, Linus Torvalds wrote: > > > On Wed, 5 May 2010, Mel Gorman wrote: > > > > If the same_vma list is properly ordered then maybe something like the > > following is allowed? > > Heh. This is the same logic I just sent out. However: > > > + anon_vma = page_rmapping(page); > > + if (!anon_vma) > > + return NULL; > > + > > + spin_lock(&anon_vma->lock); > > RCU should guarantee that this spin_lock() is valid, but: > > > + /* > > + * Get the oldest anon_vma on the list by depending on the ordering > > + * of the same_vma list setup by __page_set_anon_rmap > > + */ > > + avc = list_entry(&anon_vma->head, struct anon_vma_chain, same_anon_vma); > > We're not guaranteed that the 'anon_vma->head' list is non-empty. > > Somebody could have freed the list and the anon_vma and we have a stale > 'page->anon_vma' (that has just not been _released_ yet). > Ahh, fair point. I asked in the other mail was the empty list check necessary - it is. Thanks > And shouldn't that be 'list_first_entry'? Or &anon_vma->head.next? > Should have been list_first_entry. > How did that line actually work for you? Or was it just a "it boots", but > no actual testing of the rmap walk? > It's currently running a migration-related stress test without any deadlocks or lockdep wobbly so far. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>