[PATCH v3] ACPI: processor_idle: Fix invalid comparison with insertion sort for latency

[PATCH v3] ACPI: processor_idle: Fix invalid comparison with insertion sort for latency

[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>
---
v2 -> v3:
- Remove #include <linux/sort.h>
- Cc @stable

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 | 36 ++++++++++++++---------------------
 1 file changed, 14 insertions(+), 22 deletions(-)

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index bd6a7857ce05..17cc81340b4b 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 +385,21 @@ 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 *arr, 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;
-
-	if (!(x->valid && y->valid))
-		return;
-	swap(x->latency, y->latency);
+	for (i = 1; i < length; i++) {
+		if (!arr[i].valid)
+			continue;
+		for (j = i - 1, k = i; j >= 0; j--) {
+			if (!arr[j].valid)
+				continue;
+			if (arr[j].latency > arr[k].latency)
+				swap(arr[j].latency, arr[k].latency);
+			k = j;
+		}
+	}
 }
 
 static int acpi_processor_power_verify(struct acpi_processor *pr)
@@ -449,10 +444,7 @@ 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);
-- 
2.34.1

Re: [PATCH v3] ACPI: processor_idle: Fix invalid comparison with insertion sort for latency

[Rafael J. Wysocki]

On Mon, Jul 1, 2024 at 6:10 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>
> ---
> v2 -> v3:
> - Remove #include <linux/sort.h>
> - Cc @stable
>
> 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 | 36 ++++++++++++++---------------------
>  1 file changed, 14 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index bd6a7857ce05..17cc81340b4b 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 +385,21 @@ 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 *arr, size_t length)

s/arr/states/ please.

>  {
> -       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;
> -
> -       if (!(x->valid && y->valid))
> -               return;
> -       swap(x->latency, y->latency);
> +       for (i = 1; i < length; i++) {
> +               if (!arr[i].valid)
> +                       continue;

Please add an empty line here (and analogously below).

> +               for (j = i - 1, k = i; j >= 0; j--) {
> +                       if (!arr[j].valid)
> +                               continue;
> +                       if (arr[j].latency > arr[k].latency)
> +                               swap(arr[j].latency, arr[k].latency);

And here.

> +                       k = j;
> +               }
> +       }
>  }
>
>  static int acpi_processor_power_verify(struct acpi_processor *pr)
> @@ -449,10 +444,7 @@ 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);
> --

[PATCH v4] ACPI: processor_idle: Fix invalid comparison with insertion sort for latency

[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.

 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);
-- 
2.34.1

Re: [PATCH v4] ACPI: processor_idle: Fix invalid comparison with insertion sort for latency

[Julian Sikorski]

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);

Re: [PATCH v4] ACPI: processor_idle: Fix invalid comparison with insertion sort for latency

[Mario Limonciello]

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);
> 

Re: [PATCH v4] ACPI: processor_idle: Fix invalid comparison with insertion sort for latency

[Rafael J. Wysocki]

On 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!