From 340b42b3b21c88ebffb0e2f59f315692fc1af656 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Tue, 1 Jun 2021 22:18:22 +0800
Subject: [PATCH] cpuidle: poll_state: Revise loop termination condition
mainline inclusion
from mainline-4.20
commit 01bad1c6896db021db82042e71c2bf1f97cc026b
category: feature
bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=34
CVE: NA
If need_resched() returns "false", breaking out of the loop in
poll_idle() will cause a new idle state to be selected, so in fact
it usually doesn't make sense to spin in it longer than the target
residency of the second state. [Note that the "polling" state is
used only if there is at least one "real" state defined in addition
to it, so the second state is always there.] On the other hand,
breaking out of it early (say in case the next state is disabled)
shouldn't hurt as it is polling anyway.
For this reason, make the loop in poll_idle() break if the CPU has
been spinning longer than the target residency of the second state
(the "polling" state can only be state[0]).
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Yubo Miao <miaoyubo@huawei.com>
Signed-off-by: Xiangyou Xie <xiexiangyou@huawei.com>
Reviewed-by: Hailiang Zhang <zhang.zhanghailiang@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Jiajun Chen <chenjiajun8@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
drivers/cpuidle/poll_state.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/cpuidle/poll_state.c b/drivers/cpuidle/poll_state.c
index 36ff5a1d9422..1a00353a5c4b 100644
--- a/drivers/cpuidle/poll_state.c
+++ b/drivers/cpuidle/poll_state.c
@@ -9,7 +9,6 @@
#include <linux/sched/clock.h>
#include <linux/sched/idle.h>
-#define POLL_IDLE_TIME_LIMIT (TICK_NSEC / 16)
#define POLL_IDLE_RELAX_COUNT 200
static int __cpuidle poll_idle(struct cpuidle_device *dev,
@@ -21,6 +20,8 @@ static int __cpuidle poll_idle(struct cpuidle_device *dev,
local_irq_enable();
if (!current_set_polling_and_test()) {
+ u64 limit = (u64)drv->states[1].target_residency
+ * NSEC_PER_USEC;
unsigned int loop_count = 0;
while (!need_resched()) {
@@ -29,7 +30,7 @@ static int __cpuidle poll_idle(struct cpuidle_device *dev,
continue;
loop_count = 0;
- if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT) {
+ if (local_clock() - time_start > limit) {
dev->poll_time_limit = true;
break;
}
--
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