Gregory Price <gregory.price@xxxxxxxxxxxx> writes:
> 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;
IIUC, "node" may be used without initialization.
--
Best Regards,
Huang, Ying
> + 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;
