Thread (7 messages) 7 messages, 3 authors, 2020-06-25

Re: [PATCH 2/2][v3] PM / s2idle: Code cleanup to make s2idle consistent with normal idle path

From: Chen Yu <yu.c.chen@intel.com>
Date: 2020-06-25 05:14:36
Also in: lkml

Hi Rafael,
On Tue, Jun 23, 2020 at 07:57:59PM +0200, Rafael J. Wysocki wrote:
quoted hunk ↗ jump to hunk
From: Rafael J. Wysocki <redacted>
Subject: [PATCH] cpuidle: Rearrange s2idle-specific idle state entry code

Implement call_cpuidle_s2idle() in analogy with call_cpuidle()
for the s2idle-specific idle state entry and invoke it from
cpuidle_idle_call() to make the s2idle-specific idle entry code
path look more similar to the "regular" idle entry one.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <redacted>
---
 drivers/cpuidle/cpuidle.c |    6 +++---
 kernel/sched/idle.c       |   15 +++++++++++----
 2 files changed, 14 insertions(+), 7 deletions(-)

Index: linux-pm/kernel/sched/idle.c
===================================================================
--- linux-pm.orig/kernel/sched/idle.c
+++ linux-pm/kernel/sched/idle.c
@@ -96,6 +96,15 @@ void __cpuidle default_idle_call(void)
 	}
 }
 
+static int call_cpuidle_s2idle(struct cpuidle_driver *drv,
+			       struct cpuidle_device *dev)
+{
+	if (current_clr_polling_and_test())
+		return -EBUSY;
+
+	return cpuidle_enter_s2idle(drv, dev);
+}
+
 static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		      int next_state)
 {
@@ -171,11 +180,9 @@ static void cpuidle_idle_call(void)
 		if (idle_should_enter_s2idle()) {
 			rcu_idle_enter();
 
-			entered_state = cpuidle_enter_s2idle(drv, dev);
-			if (entered_state > 0) {
-				local_irq_enable();
+			entered_state = call_cpuidle_s2idle(drv, dev);
I guess this changes the context a little bit that(comparing to [1/2 patch],
after this modification, when we found that TIF_NEED_RESCHED is set we can have
a second chance in the following call_cpuidle to do a second s2idle try. However
in [1/2 patch], it might exit the s2idle phase directly once when we see
TIF_NEED_RESCHED is set(because entered_state is postive we treat it as a successful
s2idle). In summary I think the change (patch [2/2]) is more robust.
Acked-by: Chen Yu <yu.c.chen@intel.com>

Thanks,
Chenyu
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