linux-kernel - [PATCH] PM: QoS: Invalidate frequency QoS requests after removal

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Date:   Wed, 20 Nov 2019 10:33:34 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PM <linux-pm@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Doug Smythies <dsmythies@...us.net>,
        Leonard Crestez <leonard.crestez@....com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: [PATCH] PM: QoS: Invalidate frequency QoS requests after removal

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

Switching cpufreq drivers (or switching operation modes of the
intel_pstate driver from "active" to "passive" and vice versa)
does not work on some x86 systems with ACPI after commit
3000ce3c52f8 ("cpufreq: Use per-policy frequency QoS"), because
the ACPI _PPC and thermal code uses the same frequency QoS request
object for a given CPU every time a cpufreq driver is registered
and freq_qos_remove_request() does not invalidate the request after
removing it from its QoS list, so freq_qos_add_request() complains
and fails when that request is passed to it again.

Fix the issue by modifying freq_qos_remove_request() to clear the qos
and type fields of the frequency request pointed to by its argument
after removing it from its QoS list so as to invalidate it.

Fixes: 3000ce3c52f8 ("cpufreq: Use per-policy frequency QoS")
Reported-and-tested-by: Doug Smythies <dsmythies@...us.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 kernel/power/qos.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Index: linux-pm/kernel/power/qos.c
===================================================================
--- linux-pm.orig/kernel/power/qos.c
+++ linux-pm/kernel/power/qos.c
@@ -814,6 +814,8 @@ EXPORT_SYMBOL_GPL(freq_qos_update_reques
  */
 int freq_qos_remove_request(struct freq_qos_request *req)
 {
+	int ret;
+
 	if (!req)
 		return -EINVAL;

@@ -821,7 +823,11 @@ int freq_qos_remove_request(struct freq_
 		 "%s() called for unknown object\n", __func__))
 		return -EINVAL;

-	return freq_qos_apply(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
+	ret = freq_qos_apply(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
+	req->qos = NULL;
+	req->type = 0;
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(freq_qos_remove_request);