linux-kernel - Re: broken suspend (sched related) [Was: 2.6.24-rc4-mm1]

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Date:	Sun, 9 Dec 2007 09:06:19 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>
Subject: Re: broken suspend (sched related) [Was: 2.6.24-rc4-mm1]


* Jiri Slaby <jirislaby@...il.com> wrote:

> On 12/08/2007 04:24 PM, Ingo Molnar wrote:
> > i'm wondering why it had no effect now - the new code is in essence a 
> > NOP over what we had.
> 
> Maybe a dumb question. Why those changes in process_32.c in the patch 
> and not in process_64.c?

not a dumb question at all - i forgot about it. Find the updated patch 
below.

( sidenote: this shows the x86 unification concept in action. You
  noticed the missing _64.c probably because you saw a _32.c file 
  modified in the patch and the rule is that if we modify a _32.c file 
  then the matching _64.c file needs to be updated too. If this had been
  an old-style pre-unification arch/i386/kernel/process.c file you'd not
  have been able to tell this from just looking at the patch file - and
  we'd possibly have missed to include a fix on the 64-bit side. With
  the unification of files we are realizing it how many times this
  happened in the past (and went unnoticed). )

	Ingo

--------------------->
Subject: x86: idle wakeup event in the HLT loop
From: Ingo Molnar <mingo@...e.hu>

do a proper idle-wakeup event on HLT as well - some CPUs stop the TSC
in HLT too, not just when going through the ACPI methods.

(the ACPI idle code already does this.)

[ update the 64-bit side too, as noticed by Jiri Slaby. ]

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/x86/kernel/process_32.c |   15 ++++++++++++---
 arch/x86/kernel/process_64.c |   13 ++++++++++---
 2 files changed, 22 insertions(+), 6 deletions(-)

Index: linux-x86.q/arch/x86/kernel/process_32.c
===================================================================
--- linux-x86.q.orig/arch/x86/kernel/process_32.c
+++ linux-x86.q/arch/x86/kernel/process_32.c
@@ -113,10 +113,19 @@ void default_idle(void)
 		smp_mb();
 
 		local_irq_disable();
-		if (!need_resched())
+		if (!need_resched()) {
+			ktime_t t0, t1;
+			u64 t0n, t1n;
+
+			t0 = ktime_get();
+			t0n = ktime_to_ns(t0);
 			safe_halt();	/* enables interrupts racelessly */
-		else
-			local_irq_enable();
+			local_irq_disable();
+			t1 = ktime_get();
+			t1n = ktime_to_ns(t1);
+			sched_clock_idle_wakeup_event(t1n - t0n);
+		}
+		local_irq_enable();
 		current_thread_info()->status |= TS_POLLING;
 	} else {
 		/* loop is done by the caller */
Index: linux-x86.q/arch/x86/kernel/process_64.c
===================================================================
--- linux-x86.q.orig/arch/x86/kernel/process_64.c
+++ linux-x86.q/arch/x86/kernel/process_64.c
@@ -116,9 +116,16 @@ static void default_idle(void)
 	smp_mb();
 	local_irq_disable();
 	if (!need_resched()) {
-		/* Enables interrupts one instruction before HLT.
-		   x86 special cases this so there is no race. */
-		safe_halt();
+		ktime_t t0, t1;
+		u64 t0n, t1n;
+
+		t0 = ktime_get();
+		t0n = ktime_to_ns(t0);
+		safe_halt();	/* enables interrupts racelessly */
+		local_irq_disable();
+		t1 = ktime_get();
+		t1n = ktime_to_ns(t1);
+		sched_clock_idle_wakeup_event(t1n - t0n);
 	} else
 		local_irq_enable();
 	current_thread_info()->status |= TS_POLLING;
--
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