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

Ingo Molnar
2007-12-09T08:07:15Z

* Jiri Slaby <jirislaby@gmail.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@elte.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@elte.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;