drivers/acpi/processor_idle.c | 37 +++++++++++++++-------------------- 1 file changed, 16 insertions(+), 21 deletions(-)
The acpi_cst_latency_cmp comparison function currently used for sorting
C-state latencies does not satisfy transitivity, causing incorrect
sorting results. Specifically, if there are two valid acpi_processor_cx
elements A and B and one invalid element C, it may occur that A < B,
A = C, and B = C. Sorting algorithms assume that if A < B and A = C,
then C < B, leading to incorrect ordering.
Given the small size of the array (<=8), we replace the library sort
function with a simple insertion sort that properly ignores invalid
elements and sorts valid ones based on latency. This change ensures
correct ordering of the C-state latencies.
Fixes: 65ea8f2c6e23 ("ACPI: processor idle: Fix up C-state latency if not ordered")
Cc: stable@vger.kernel.org
Reported-by: Julian Sikorski <belegdol@gmail.com>
Closes: https://lore.kernel.org/lkml/70674dc7-5586-4183-8953-8095567e73df@gmail.com/
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
---
v3 -> v4:
- Rename the parameter 'arr' to 'states'.
- Add empty lines to enhance readability.
Note: I only performed a build test and a simple unit test to ensure
the latency of valid elements is correctly sorted in the randomly
generated data.
drivers/acpi/processor_idle.c | 37 +++++++++++++++--------------------
1 file changed, 16 insertions(+), 21 deletions(-)
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index bd6a7857ce05..831fa4a12159 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -16,7 +16,6 @@
#include <linux/acpi.h>
#include <linux/dmi.h>
#include <linux/sched.h> /* need_resched() */
-#include <linux/sort.h>
#include <linux/tick.h>
#include <linux/cpuidle.h>
#include <linux/cpu.h>
@@ -386,25 +385,24 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
acpi_write_bit_register(ACPI_BITREG_BUS_MASTER_RLD, 1);
}
-static int acpi_cst_latency_cmp(const void *a, const void *b)
+static void acpi_cst_latency_sort(struct acpi_processor_cx *states, size_t length)
{
- const struct acpi_processor_cx *x = a, *y = b;
+ int i, j, k;
- if (!(x->valid && y->valid))
- return 0;
- if (x->latency > y->latency)
- return 1;
- if (x->latency < y->latency)
- return -1;
- return 0;
-}
-static void acpi_cst_latency_swap(void *a, void *b, int n)
-{
- struct acpi_processor_cx *x = a, *y = b;
+ for (i = 1; i < length; i++) {
+ if (!states[i].valid)
+ continue;
- if (!(x->valid && y->valid))
- return;
- swap(x->latency, y->latency);
+ for (j = i - 1, k = i; j >= 0; j--) {
+ if (!states[j].valid)
+ continue;
+
+ if (states[j].latency > states[k].latency)
+ swap(states[j].latency, states[k].latency);
+
+ k = j;
+ }
+ }
}
static int acpi_processor_power_verify(struct acpi_processor *pr)
@@ -449,10 +447,7 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)
if (buggy_latency) {
pr_notice("FW issue: working around C-state latencies out of order\n");
- sort(&pr->power.states[1], max_cstate,
- sizeof(struct acpi_processor_cx),
- acpi_cst_latency_cmp,
- acpi_cst_latency_swap);
+ acpi_cst_latency_sort(&pr->power.states[1], max_cstate);
}
lapic_timer_propagate_broadcast(pr);
--
2.34.1On Mon, Jul 1, 2024 at 10:56 PM Kuan-Wei Chiu <visitorckw@gmail.com> wrote:
>
> The acpi_cst_latency_cmp comparison function currently used for sorting
> C-state latencies does not satisfy transitivity, causing incorrect
> sorting results. Specifically, if there are two valid acpi_processor_cx
> elements A and B and one invalid element C, it may occur that A < B,
> A = C, and B = C. Sorting algorithms assume that if A < B and A = C,
> then C < B, leading to incorrect ordering.
>
> Given the small size of the array (<=8), we replace the library sort
> function with a simple insertion sort that properly ignores invalid
> elements and sorts valid ones based on latency. This change ensures
> correct ordering of the C-state latencies.
>
> Fixes: 65ea8f2c6e23 ("ACPI: processor idle: Fix up C-state latency if not ordered")
> Cc: stable@vger.kernel.org
> Reported-by: Julian Sikorski <belegdol@gmail.com>
> Closes: https://lore.kernel.org/lkml/70674dc7-5586-4183-8953-8095567e73df@gmail.com/
> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
> ---
> v3 -> v4:
> - Rename the parameter 'arr' to 'states'.
> - Add empty lines to enhance readability.
>
> Note: I only performed a build test and a simple unit test to ensure
> the latency of valid elements is correctly sorted in the randomly
> generated data.
>
> drivers/acpi/processor_idle.c | 37 +++++++++++++++--------------------
> 1 file changed, 16 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index bd6a7857ce05..831fa4a12159 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -16,7 +16,6 @@
> #include <linux/acpi.h>
> #include <linux/dmi.h>
> #include <linux/sched.h> /* need_resched() */
> -#include <linux/sort.h>
> #include <linux/tick.h>
> #include <linux/cpuidle.h>
> #include <linux/cpu.h>
> @@ -386,25 +385,24 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
> acpi_write_bit_register(ACPI_BITREG_BUS_MASTER_RLD, 1);
> }
>
> -static int acpi_cst_latency_cmp(const void *a, const void *b)
> +static void acpi_cst_latency_sort(struct acpi_processor_cx *states, size_t length)
> {
> - const struct acpi_processor_cx *x = a, *y = b;
> + int i, j, k;
>
> - if (!(x->valid && y->valid))
> - return 0;
> - if (x->latency > y->latency)
> - return 1;
> - if (x->latency < y->latency)
> - return -1;
> - return 0;
> -}
> -static void acpi_cst_latency_swap(void *a, void *b, int n)
> -{
> - struct acpi_processor_cx *x = a, *y = b;
> + for (i = 1; i < length; i++) {
> + if (!states[i].valid)
> + continue;
>
> - if (!(x->valid && y->valid))
> - return;
> - swap(x->latency, y->latency);
> + for (j = i - 1, k = i; j >= 0; j--) {
> + if (!states[j].valid)
> + continue;
> +
> + if (states[j].latency > states[k].latency)
> + swap(states[j].latency, states[k].latency);
> +
> + k = j;
> + }
> + }
> }
>
> static int acpi_processor_power_verify(struct acpi_processor *pr)
> @@ -449,10 +447,7 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)
>
> if (buggy_latency) {
> pr_notice("FW issue: working around C-state latencies out of order\n");
> - sort(&pr->power.states[1], max_cstate,
> - sizeof(struct acpi_processor_cx),
> - acpi_cst_latency_cmp,
> - acpi_cst_latency_swap);
> + acpi_cst_latency_sort(&pr->power.states[1], max_cstate);
> }
>
> lapic_timer_propagate_broadcast(pr);
> --
Applied as 6.10-rc material, thanks!
Am 01.07.24 um 22:56 schrieb Kuan-Wei Chiu:
> The acpi_cst_latency_cmp comparison function currently used for sorting
> C-state latencies does not satisfy transitivity, causing incorrect
> sorting results. Specifically, if there are two valid acpi_processor_cx
> elements A and B and one invalid element C, it may occur that A < B,
> A = C, and B = C. Sorting algorithms assume that if A < B and A = C,
> then C < B, leading to incorrect ordering.
>
> Given the small size of the array (<=8), we replace the library sort
> function with a simple insertion sort that properly ignores invalid
> elements and sorts valid ones based on latency. This change ensures
> correct ordering of the C-state latencies.
>
> Fixes: 65ea8f2c6e23 ("ACPI: processor idle: Fix up C-state latency if not ordered")
> Cc: stable@vger.kernel.org
> Reported-by: Julian Sikorski <belegdol@gmail.com>
> Closes: https://lore.kernel.org/lkml/70674dc7-5586-4183-8953-8095567e73df@gmail.com/
> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
> ---
> v3 -> v4:
> - Rename the parameter 'arr' to 'states'.
> - Add empty lines to enhance readability.
>
> Note: I only performed a build test and a simple unit test to ensure
> the latency of valid elements is correctly sorted in the randomly
> generated data.
>
Hello,
thanks for the patch. I have tested this applied on top of Fedora 6.9.7
kernel on my Asus laptop and the message about suspend not reaching the
deepest state is gone. Thank you.
I wonder whether this will also fix random S3 suspend issues I have been
seeing on my 5600x since 6.9 kernel too. I will definitely try.
Best regards,
Julian
Tested-by: Julian Sikorski <belegdol@gmail.com>
> drivers/acpi/processor_idle.c | 37 +++++++++++++++--------------------
> 1 file changed, 16 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index bd6a7857ce05..831fa4a12159 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -16,7 +16,6 @@
> #include <linux/acpi.h>
> #include <linux/dmi.h>
> #include <linux/sched.h> /* need_resched() */
> -#include <linux/sort.h>
> #include <linux/tick.h>
> #include <linux/cpuidle.h>
> #include <linux/cpu.h>
> @@ -386,25 +385,24 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr,
> acpi_write_bit_register(ACPI_BITREG_BUS_MASTER_RLD, 1);
> }
>
> -static int acpi_cst_latency_cmp(const void *a, const void *b)
> +static void acpi_cst_latency_sort(struct acpi_processor_cx *states, size_t length)
> {
> - const struct acpi_processor_cx *x = a, *y = b;
> + int i, j, k;
>
> - if (!(x->valid && y->valid))
> - return 0;
> - if (x->latency > y->latency)
> - return 1;
> - if (x->latency < y->latency)
> - return -1;
> - return 0;
> -}
> -static void acpi_cst_latency_swap(void *a, void *b, int n)
> -{
> - struct acpi_processor_cx *x = a, *y = b;
> + for (i = 1; i < length; i++) {
> + if (!states[i].valid)
> + continue;
>
> - if (!(x->valid && y->valid))
> - return;
> - swap(x->latency, y->latency);
> + for (j = i - 1, k = i; j >= 0; j--) {
> + if (!states[j].valid)
> + continue;
> +
> + if (states[j].latency > states[k].latency)
> + swap(states[j].latency, states[k].latency);
> +
> + k = j;
> + }
> + }
> }
>
> static int acpi_processor_power_verify(struct acpi_processor *pr)
> @@ -449,10 +447,7 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)
>
> if (buggy_latency) {
> pr_notice("FW issue: working around C-state latencies out of order\n");
> - sort(&pr->power.states[1], max_cstate,
> - sizeof(struct acpi_processor_cx),
> - acpi_cst_latency_cmp,
> - acpi_cst_latency_swap);
> + acpi_cst_latency_sort(&pr->power.states[1], max_cstate);
> }
>
> lapic_timer_propagate_broadcast(pr);
On 7/2/2024 2:28, Julian Sikorski wrote:
> Am 01.07.24 um 22:56 schrieb Kuan-Wei Chiu:
>> The acpi_cst_latency_cmp comparison function currently used for sorting
>> C-state latencies does not satisfy transitivity, causing incorrect
>> sorting results. Specifically, if there are two valid acpi_processor_cx
>> elements A and B and one invalid element C, it may occur that A < B,
>> A = C, and B = C. Sorting algorithms assume that if A < B and A = C,
>> then C < B, leading to incorrect ordering.
>>
>> Given the small size of the array (<=8), we replace the library sort
>> function with a simple insertion sort that properly ignores invalid
>> elements and sorts valid ones based on latency. This change ensures
>> correct ordering of the C-state latencies.
>>
>> Fixes: 65ea8f2c6e23 ("ACPI: processor idle: Fix up C-state latency if
>> not ordered")
>> Cc: stable@vger.kernel.org
>> Reported-by: Julian Sikorski <belegdol@gmail.com>
>> Closes:
>> https://lore.kernel.org/lkml/70674dc7-5586-4183-8953-8095567e73df@gmail.com/
>> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
>> ---
>> v3 -> v4:
>> - Rename the parameter 'arr' to 'states'.
>> - Add empty lines to enhance readability.
>>
>> Note: I only performed a build test and a simple unit test to ensure
>> the latency of valid elements is correctly sorted in the randomly
>> generated data.
>>
>
> Hello,
>
> thanks for the patch. I have tested this applied on top of Fedora 6.9.7
> kernel on my Asus laptop and the message about suspend not reaching the
> deepest state is gone. Thank you.
That's great news.
> I wonder whether this will also fix random S3 suspend issues I have been
> seeing on my 5600x since 6.9 kernel too. I will definitely try.
Does your 5600x also sort C states? You'll see message in the logs. If
so yes it could help. If not; you probably will need to bisect that
separately.
>
> Best regards,
> Julian
>
> Tested-by: Julian Sikorski <belegdol@gmail.com>
>
>> drivers/acpi/processor_idle.c | 37 +++++++++++++++--------------------
>> 1 file changed, 16 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/acpi/processor_idle.c
>> b/drivers/acpi/processor_idle.c
>> index bd6a7857ce05..831fa4a12159 100644
>> --- a/drivers/acpi/processor_idle.c
>> +++ b/drivers/acpi/processor_idle.c
>> @@ -16,7 +16,6 @@
>> #include <linux/acpi.h>
>> #include <linux/dmi.h>
>> #include <linux/sched.h> /* need_resched() */
>> -#include <linux/sort.h>
>> #include <linux/tick.h>
>> #include <linux/cpuidle.h>
>> #include <linux/cpu.h>
>> @@ -386,25 +385,24 @@ static void
>> acpi_processor_power_verify_c3(struct acpi_processor *pr,
>> acpi_write_bit_register(ACPI_BITREG_BUS_MASTER_RLD, 1);
>> }
>> -static int acpi_cst_latency_cmp(const void *a, const void *b)
>> +static void acpi_cst_latency_sort(struct acpi_processor_cx *states,
>> size_t length)
>> {
>> - const struct acpi_processor_cx *x = a, *y = b;
>> + int i, j, k;
>> - if (!(x->valid && y->valid))
>> - return 0;
>> - if (x->latency > y->latency)
>> - return 1;
>> - if (x->latency < y->latency)
>> - return -1;
>> - return 0;
>> -}
>> -static void acpi_cst_latency_swap(void *a, void *b, int n)
>> -{
>> - struct acpi_processor_cx *x = a, *y = b;
>> + for (i = 1; i < length; i++) {
>> + if (!states[i].valid)
>> + continue;
>> - if (!(x->valid && y->valid))
>> - return;
>> - swap(x->latency, y->latency);
>> + for (j = i - 1, k = i; j >= 0; j--) {
>> + if (!states[j].valid)
>> + continue;
>> +
>> + if (states[j].latency > states[k].latency)
>> + swap(states[j].latency, states[k].latency);
>> +
>> + k = j;
>> + }
>> + }
>> }
>> static int acpi_processor_power_verify(struct acpi_processor *pr)
>> @@ -449,10 +447,7 @@ static int acpi_processor_power_verify(struct
>> acpi_processor *pr)
>> if (buggy_latency) {
>> pr_notice("FW issue: working around C-state latencies out of
>> order\n");
>> - sort(&pr->power.states[1], max_cstate,
>> - sizeof(struct acpi_processor_cx),
>> - acpi_cst_latency_cmp,
>> - acpi_cst_latency_swap);
>> + acpi_cst_latency_sort(&pr->power.states[1], max_cstate);
>> }
>> lapic_timer_propagate_broadcast(pr);
>
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