linux-kernel - Re: [PATCH 34/35] tick: Provide tick_suspend

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Message-ID: <20150218133524.GU5029@twins.programming.kicks-ass.net>
Date:	Wed, 18 Feb 2015 14:35:24 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Nicolas Pitre <nico@...aro.org>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [PATCH 34/35] tick: Provide tick_suspend_local()

On Tue, Feb 17, 2015 at 02:31:42PM +0000, Lorenzo Pieralisi wrote:
> On Mon, Feb 16, 2015 at 12:15:09PM +0000, Peter Zijlstra wrote:
> > From: Thomas Gleixner <tglx@...utronix.de>
> > 
> > This function is intended to use by the freezer once the freezer folks
> > solved their race issues. Also required to get rid of the ARM BL
> > switcher tick hackery.
> 
> Totally agree with the patch(es), but I noticed that the ARM bL switcher
> does not depend on PM_SLEEP, so I do not think you can compile
> tick_{suspend/resume}_local() out if !PM_SLEEP, unless dependency
> is enforced by the ARM bL switcher config but I do not think that
> the config dependency really exists, Nico please correct me if I am
> wrong.

Ah I see, the headers seem to do the right thing and declare the
function in core (GENERIC_CLOCKEVENTS) with a comment.

But then the patch continues defining the functions under PM_SLEEP.

I wonder why the build robot has not reported fail on this..

Would the below make sense?

---
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -368,7 +368,6 @@ void tick_shutdown_local(void)
 }
 #endif
 
-#ifdef CONFIG_PM_SLEEP
 /**
  * tick_suspend_local - Suspend the local tick device
  *
@@ -384,20 +383,6 @@ void tick_suspend_local(void)
 }
 
 /**
- * tick_suspend - Suspend the tick and the broadcast device
- *
- * Called from syscore_suspend() via timekeeping_suspend with only one
- * CPU online and interrupts disabled.
- *
- * No locks required. Nothing can change the per cpu device.
- */
-void tick_suspend(void)
-{
-	tick_suspend_local();
-	tick_suspend_broadcast();
-}
-
-/**
  * tick_resume_local - Resume the local tick device
  *
  * Called from the local cpu for unfreeze or XEN resume magic
@@ -418,6 +403,21 @@ void tick_resume_local(void)
 	}
 }
 
+#ifdef CONFIG_PM_SLEEP
+/**
+ * tick_suspend - Suspend the tick and the broadcast device
+ *
+ * Called from syscore_suspend() via timekeeping_suspend with only one
+ * CPU online and interrupts disabled.
+ *
+ * No locks required. Nothing can change the per cpu device.
+ */
+void tick_suspend(void)
+{
+	tick_suspend_local();
+	tick_suspend_broadcast();
+}
+
 /**
  * tick_resume - Resume the tick and the broadcast device
  *
--
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