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Commit cfcdc6f6 authored by Kuan-Wei Chiu's avatar Kuan-Wei Chiu Committed by Greg Kroah-Hartman
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ACPI: processor_idle: Fix invalid comparison with insertion sort for latency 



commit 233323f9b9f828cd7cd5145ad811c1990b692542 upstream.

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")
Reported-by: default avatarJulian Sikorski <belegdol@gmail.com>
Closes: https://lore.kernel.org/lkml/70674dc7-5586-4183-8953-8095567e73df@gmail.com


Signed-off-by: default avatarKuan-Wei Chiu <visitorckw@gmail.com>
Tested-by: default avatarJulian Sikorski <belegdol@gmail.com>
Cc: All applicable <stable@vger.kernel.org>
Link: https://patch.msgid.link/20240701205639.117194-1-visitorckw@gmail.com


Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: default avatarKuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 281e90e3

drivers/acpi/processor_idle.c

+16 −24
Original line number Original line Diff line number Diff line
@@ -16,7 +16,6 @@ 
#include <linux/acpi.h>

#include <linux/acpi.h>

#include <linux/dmi.h>

#include <linux/dmi.h>

#include <linux/sched.h>       /* need_resched() */

#include <linux/sched.h>       /* need_resched() */

#include <linux/sort.h>

#include <linux/tick.h>

#include <linux/tick.h>

#include <linux/cpuidle.h>

#include <linux/cpuidle.h>

#include <linux/cpu.h>

#include <linux/cpu.h>
@@ -541,28 +540,24 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr, 
	return;

	return;

}

}





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))

	for (i = 1; i < length; i++) {

		return 0;

		if (!states[i].valid)

	if (x->latency > y->latency)

			continue;

		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;

	u32 tmp;





	if (!(x->valid && y->valid))

		for (j = i - 1, k = i; j >= 0; j--) {

		return;

			if (!states[j].valid)

	tmp = x->latency;

				continue;

	x->latency = y->latency;



	y->latency = tmp;

			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)

static int acpi_processor_power_verify(struct acpi_processor *pr)
@@ -607,10 +602,7 @@ static int acpi_processor_power_verify(struct acpi_processor *pr) 




	if (buggy_latency) {

	if (buggy_latency) {

		pr_notice("FW issue: working around C-state latencies out of order\n");

		pr_notice("FW issue: working around C-state latencies out of order\n");

		sort(&pr->power.states[1], max_cstate,

		acpi_cst_latency_sort(&pr->power.states[1], max_cstate);

		     sizeof(struct acpi_processor_cx),

		     acpi_cst_latency_cmp,

		     acpi_cst_latency_swap);

	}

	}





	lapic_timer_propagate_broadcast(pr);

	lapic_timer_propagate_broadcast(pr);