On Wed, Nov 16, 2022 at 12:57:36AM -0700, Vishal Verma wrote:
> In a system with a single initiator node, and one or more memory-only
> 'target' nodes, the memory-only node(s) would fail to register their
> initiator node correctly. i.e. in sysfs:
>
> # ls /sys/devices/system/node/node0/access0/targets/
> node0
>
> Where as the correct behavior should be:
>
> # ls /sys/devices/system/node/node0/access0/targets/
> node0 node1
>
> This happened because hmat_register_target_initiators() uses list_sort()
> to sort the initiator list, but the sort comparision function
> (initiator_cmp()) is overloaded to also set the node mask's bits.
>
> In a system with a single initiator, the list is singular, and list_sort
> elides the comparision helper call. Thus the node mask never gets set,
> and the subsequent search for the best initiator comes up empty.
>
> Add a new helper to sort the initiator list, and handle the singular
> list corner case by setting the node mask for that explicitly.
>
> Reported-by: Chris Piper <chris.d.piper@xxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Cc: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> Cc: Liu Shixin <liushixin2@xxxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> ---
> drivers/acpi/numa/hmat.c | 32 ++++++++++++++++++++++++++++++--
> 1 file changed, 30 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
> index 144a84f429ed..cd20b0e9cdfa 100644
> --- a/drivers/acpi/numa/hmat.c
> +++ b/drivers/acpi/numa/hmat.c
> @@ -573,6 +573,30 @@ static int initiator_cmp(void *priv, const struct list_head *a,
> return ia->processor_pxm - ib->processor_pxm;
> }
>
> +static int initiators_to_nodemask(unsigned long *p_nodes)
> +{
> + /*
> + * list_sort doesn't call @cmp (initiator_cmp) for 0 or 1 sized lists.
> + * For a single-initiator system with other memory-only nodes, this
> + * means an empty p_nodes mask, since that is set by initiator_cmp().
> + * Special case the singular list, and make sure the node mask gets set
> + * appropriately.
> + */
> + if (list_empty(&initiators))
> + return -ENXIO;
> +
> + if (list_is_singular(&initiators)) {
> + struct memory_initiator *initiator = list_first_entry(
> + &initiators, struct memory_initiator, node);
> +
> + set_bit(initiator->processor_pxm, p_nodes);
> + return 0;
> + }
> +
> + list_sort(p_nodes, &initiators, initiator_cmp);
> + return 0;
> +}
> +
Hm. I think it indicates that these set_bit()s do not belong to
initiator_cmp().
Maybe remove both set_bit() from the compare helper and walk the list
separately to initialize the node mask? I think it will be easier to
follow.
--
Kiryl Shutsemau / Kirill A. Shutemov
