On Tue, 18 Oct 2016 16:56:48 -0400 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > Is releasing the lock within a llist_for_each_entry_safe() actually safe? Is > vmap_area_lock the one to protect the valist? > > That is llist_for_each_entry_safe(va, n_va, valist, purg_list) does: > > for (va = llist_entry(valist, typeof(*va), purge_list); > &va->purge_list != NULL && > n_va = llist_entry(va->purge_list.next, typeof(*n_va), > purge_list, true); > pos = n) > > Thus n_va is pointing to the next element to process when we release the > lock. Is it possible for another task to get into this same path and process > the item that n_va is pointing to? Then when the preempted task comes back, > grabs the vmap_area_lock, and then continues the loop with what n_va has, > could that cause problems? That is, the next iteration after releasing the > lock does va = n_va. What happens if n_va no longer exits? > > I don't know this code that well, and perhaps vmap_area_lock is not protecting > the list and this is all fine. > Bah, nevermind. I missed the: valist = llist_del_all(&vmap_purge_list); so yeah, all should be good. Nothing to see here, move along please. -- Steve -- 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>