The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y git checkout FETCH_HEAD git cherry-pick -x 233323f9b9f828cd7cd5145ad811c1990b692542 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024071531-underpaid-plop-ac0c@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

233323f9b9f8 ("ACPI: processor_idle: Fix invalid comparison with insertion sort for latency") 0e6078c3c673 ("ACPI: processor idle: Use swap() instead of open coding it") 65ea8f2c6e23 ("ACPI: processor idle: Fix up C-state latency if not ordered")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 233323f9b9f828cd7cd5145ad811c1990b692542 Mon Sep 17 00:00:00 2001 From: Kuan-Wei Chiu visitorckw@gmail.com Date: Tue, 2 Jul 2024 04:56:39 +0800 Subject: [PATCH] ACPI: processor_idle: Fix invalid comparison with insertion sort for latency

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: 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 Tested-by: Julian 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: Rafael J. Wysocki rafael.j.wysocki@intel.com

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);