linux-kernel - [PATCH] PM: QoS: Add check to make sure CPU latency is non-negative

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Message-ID: <20230731060354.4802-1-clive.lin@mediatek.com>
Date:   Mon, 31 Jul 2023 14:03:54 +0800
From:   Clive Lin <clive.lin@...iatek.com>
To:     <rafael@...nel.org>, <pavel@....cz>, <len.brown@...el.com>
CC:     <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <chung-kai.yang@...iatek.com>, <ccj.yeh@...iatek.com>,
        <clive.lin@...iatek.com>, <ching-hao.hsu@...iatek.com>
Subject: [PATCH] PM: QoS: Add check to make sure CPU latency is non-negative

CPU latency should never be negative, which will be incorrectly high
when converted to unsigned data type. Commit 8d36694245f2 ("PM: QoS:
Add check to make sure CPU freq is non-negative") makes sure CPU freq
is non-negative to fix incorrect behavior in freq_qos. Adding a check
to make sure CPU latency is non-negative can prevent this problem
from happening in cpu_latency_qos.

Signed-off-by: Clive Lin <clive.lin@...iatek.com>
---
 kernel/power/qos.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/power/qos.c b/kernel/power/qos.c
index 782d3b41c1f3..4244b069442e 100644
--- a/kernel/power/qos.c
+++ b/kernel/power/qos.c
@@ -220,6 +220,11 @@ static struct pm_qos_constraints cpu_latency_constraints = {
 	.type = PM_QOS_MIN,
 };
 
+static inline bool cpu_latency_qos_value_invalid(s32 value)
+{
+	return value < 0 && value != PM_QOS_DEFAULT_VALUE;
+}
+
 /**
  * cpu_latency_qos_limit - Return current system-wide CPU latency QoS limit.
  */
@@ -263,7 +268,7 @@ static void cpu_latency_qos_apply(struct pm_qos_request *req,
  */
 void cpu_latency_qos_add_request(struct pm_qos_request *req, s32 value)
 {
-	if (!req)
+	if (!req || cpu_latency_qos_value_invalid(value))
 		return;
 
 	if (cpu_latency_qos_request_active(req)) {
@@ -289,7 +294,7 @@ EXPORT_SYMBOL_GPL(cpu_latency_qos_add_request);
  */
 void cpu_latency_qos_update_request(struct pm_qos_request *req, s32 new_value)
 {
-	if (!req)
+	if (!req || cpu_latency_qos_value_invalid(new_value))
 		return;
 
 	if (!cpu_latency_qos_request_active(req)) {
-- 
2.18.0