On Thu, Feb 01, 2024 at 09:55:07AM +0800, Huang, Ying wrote: > Gregory Price <gregory.price@xxxxxxxxxxxx> writes: > > - u8 __rcu *table, *weights, weight; > > + u8 __rcu *table, __rcu *weights, weight; > > The __rcu usage can be checked with `sparse` directly. For example, > > make C=1 mm/mempolicy.o > fixed and squashed, all the __rcu usage i had except the global pointer have been used. Thanks for the reference material, was struggling to understand that. > > task->mems_allowed_seq protection (added as 4th patch) > > ------------------------------------------------------ > > > > + cpuset_mems_cookie = read_mems_allowed_begin(); > > if (!current->il_weight || !node_isset(node, policy->nodes)) { > > node = next_node_in(node, policy->nodes); > > node will be changed in the loop. So we need to change the logic here. > new patch, if it all looks good i'll ship it in v5 ~Gregory diff --git a/mm/mempolicy.c b/mm/mempolicy.c index d8cc3a577986..4e5a640d10b8 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1878,11 +1878,17 @@ bool apply_policy_zone(struct mempolicy *policy, enum zone_type zone) static unsigned int weighted_interleave_nodes(struct mempolicy *policy) { - unsigned int node = current->il_prev; - - if (!current->il_weight || !node_isset(node, policy->nodes)) { - node = next_node_in(node, policy->nodes); - /* can only happen if nodemask is being rebound */ + unsigned int node; + unsigned int cpuset_mems_cookie; + +retry: + /* to prevent miscount use tsk->mems_allowed_seq to detect rebind */ + cpuset_mems_cookie = read_mems_allowed_begin(); + if (!current->il_weight || + !node_isset(current->il_prev, policy->nodes)) { + node = next_node_in(current->il_prev, policy->nodes); + if (read_mems_allowed_retry(cpuset_mems_cookie)) + goto retry; if (node == MAX_NUMNODES) return node; current->il_prev = node; @@ -1896,8 +1902,14 @@ static unsigned int weighted_interleave_nodes(struct mempolicy *policy) static unsigned int interleave_nodes(struct mempolicy *policy) { unsigned int nid; + unsigned int cpuset_mems_cookie; + + /* to prevent miscount, use tsk->mems_allowed_seq to detect rebind */ + do { + cpuset_mems_cookie = read_mems_allowed_begin(); + nid = next_node_in(current->il_prev, policy->nodes); + } while (read_mems_allowed_retry(cpuset_mems_cookie)); - nid = next_node_in(current->il_prev, policy->nodes); if (nid < MAX_NUMNODES) current->il_prev = nid; return nid; @@ -2374,6 +2386,7 @@ static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp, struct page **page_array) { struct task_struct *me = current; + unsigned int cpuset_mems_cookie; unsigned long total_allocated = 0; unsigned long nr_allocated = 0; unsigned long rounds; @@ -2391,7 +2404,13 @@ static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp, if (!nr_pages) return 0; - nnodes = read_once_policy_nodemask(pol, &nodes); + /* read the nodes onto the stack, retry if done during rebind */ + do { + cpuset_mems_cookie = read_mems_allowed_begin(); + nnodes = read_once_policy_nodemask(pol, &nodes); + } while (read_mems_allowed_retry(cpuset_mems_cookie)); + + /* if the nodemask has become invalid, we cannot do anything */ if (!nnodes) return 0;