linux-kernel - [PATCH v1] ACPI: processor: perflib: Move problematic pr->performance check

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Message-ID: <2801421.mvXUDI8C0e@rafael.j.wysocki>
Date: Tue, 12 Aug 2025 14:57:06 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Linux ACPI <linux-acpi@...r.kernel.org>
Cc: Jiayi Li <lijiayi@...inos.cn>, LKML <linux-kernel@...r.kernel.org>,
 Linux PM <linux-pm@...r.kernel.org>,
 Mario Limonciello <mario.limonciello@....com>
Subject:
 [PATCH v1] ACPI: processor: perflib: Move problematic pr->performance check

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Commit d33bd88ac0eb ("ACPI: processor: perflib: Fix initial _PPC limit
application") added a pr->performance check that prevents the frequency
QoS request from being added when the given processor has no performance
object.  Unfortunately, this causes a WARN() in freq_qos_remove_request()
to trigger on an attempt to take the given CPU offline later because the
frequency QoS object has not been added for it due to the missing
performance object.

Address this by moving the pr->performance check before calling
acpi_processor_get_platform_limit() so it only prevents a limit from
being set for the CPU if the performance object is not present.  This
way, the frequency QoS request is added as it was before the above
commit and it is present all the time along with the CPU's cpufreq
policy regardless of whether or not the CPU is online.

Fixes: d33bd88ac0eb ("ACPI: processor: perflib: Fix initial _PPC limit application")
Tested-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: 5.4+ <stable@...r.kernel.org> # 5.4+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/acpi/processor_perflib.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -180,7 +180,7 @@
 		struct acpi_processor *pr = per_cpu(processors, cpu);
 		int ret;

-		if (!pr || !pr->performance)
+		if (!pr)
 			continue;

 		/*
@@ -197,6 +197,9 @@
 			pr_err("Failed to add freq constraint for CPU%d (%d)\n",
 			       cpu, ret);

+		if (!pr->performance)
+			continue;
+
 		ret = acpi_processor_get_platform_limit(pr);
 		if (ret)
 			pr_err("Failed to update freq constraint for CPU%d (%d)\n",