On Wed, Aug 09, 2023 at 01:54:47PM -0500, Mario Limonciello wrote:
> The constraints table should be resetting the `list` object
> after running through all of `info_obj` iterations.
This *looks* like it should fix a real problem (see below), but not
the one mentioned here. But maybe I'm missing something because the
code that looks broken to me has been there since 146f1ed852a8 ("ACPI:
PM: s2idle: Add AMD support to handle _DSM"), which appeared in v5.11
in 2021.
> This adjusts whitespace as well as less code will now be included
> with each loop.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> ---
> v9->v10:
> * split from other patches
> ---
> drivers/acpi/x86/s2idle.c | 35 +++++++++++++++++------------------
> 1 file changed, 17 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
> index ce62e61a9605e..b566b3aa09388 100644
> --- a/drivers/acpi/x86/s2idle.c
> +++ b/drivers/acpi/x86/s2idle.c
> @@ -129,12 +129,12 @@ static void lpi_device_get_constraints_amd(void)
> struct lpi_constraints *list;
> acpi_status status;
>
> + list = &lpi_constraints_table[lpi_constraints_table_size];
> + list->min_dstate = -EINVAL;
I really have no idea what's going on here, but the code still looks
weird:
1) Moving the "list" update:
for (j = 0; j < package->package.count; ++j) {
+ list = &lpi_constraints_table[lpi_constraints_table_size];
for (k = 0; k < info_obj->package.count; ++k) {
- list = &lpi_constraints_table[lpi_constraints_table_size];
...
}
lpi_constraints_table_size++;
}
looks fine, but lpi_constraints_table_size isn't updated inside
the "k" loop, and "list" isn't otherwise updated, so it shouldn't
make any functional difference.
HOWEVER, this patch also moves all the
dev_info.enabled/name/min_dstate tests outside the "k" loop, so
they're only done after the "k" loop has completed and they've
all been set, which looks like it DOES fix a problem and is not
mentioned in the commit log.
2) Both lpi_device_get_constraints_amd() and
lpi_device_get_constraints() overwrite the global
lpi_constraints_table for each PNP0D80 device. I assume there's
some higher-level constraint that there can only be one such
device, but the code doesn't enforce that.
3) It's obvious that lpi_device_get_constraints() can only allocate
lpi_constraints_table once per call. It's NOT obvious for
lpi_device_get_constraints_amd(), because the alloc is inside a
loop:
for (i = 0; i < out_obj->package.count; i++) {
lpi_constraints_table = kcalloc(...);
If the AMD _DSM returns more than one package, we'll leak all but
the last one.
4) Both lpi_device_get_constraints_amd() and
lpi_device_get_constraints() use pre- and post-increment in the
"for" loops for no apparent reason:
for (i = 0; i < out_obj->package.count; i++)
for (j = 0; j < package->package.count; ++j)
for (k = 0; k < info_obj->package.count; ++k) # AMD only
I'd say they should all use the same (I vote for post-increment).
> for (k = 0; k < info_obj->package.count; ++k) {
> union acpi_object *obj = &info_obj->package.elements[k];
>
> - list = &lpi_constraints_table[lpi_constraints_table_size];
> - list->min_dstate = -1;
> -
> switch (k) {
> case 0:
> dev_info.enabled = obj->integer.value;
> @@ -149,26 +149,25 @@ static void lpi_device_get_constraints_amd(void)
> dev_info.min_dstate = obj->integer.value;
> break;
> }
> + }
>
> - if (!dev_info.enabled || !dev_info.name ||
> - !dev_info.min_dstate)
> - continue;
> + if (!dev_info.enabled || !dev_info.name ||
> + !dev_info.min_dstate)
> + continue;
>
> - status = acpi_get_handle(NULL, dev_info.name,
> - &list->handle);
> - if (ACPI_FAILURE(status))
> - continue;
> + status = acpi_get_handle(NULL, dev_info.name, &list->handle);
> + if (ACPI_FAILURE(status))
> + continue;
>
> - acpi_handle_debug(lps0_device_handle,
> - "Name:%s\n", dev_info.name);
> + acpi_handle_debug(lps0_device_handle,
> + "Name:%s\n", dev_info.name);
>
> - list->min_dstate = dev_info.min_dstate;
> + list->min_dstate = dev_info.min_dstate;
>
> - if (list->min_dstate < 0) {
> - acpi_handle_debug(lps0_device_handle,
> - "Incomplete constraint defined\n");
> - continue;
> - }
> + if (list->min_dstate < 0) {
> + acpi_handle_debug(lps0_device_handle,
> + "Incomplete constraint defined\n");
> + continue;
> }
> lpi_constraints_table_size++;
> }
> --
> 2.34.1
>
