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SubjectRe: cpu hotplug support broken in 2.6.23-rc3
On Sat, 15 Sep 2007 11:49:41 +0200 Thomas Gleixner <tglx@linutronix.de> wrote:

> On Fri, 2007-09-14 at 15:15 +0200, Thomas Gleixner wrote:
> > > Venki sent me an initial patch, but it has issues with the notify
> > > ordering. Find below my "cache the broadcast flags" version for testing.
> >
> > Hmmpf, the flag is still cleared when the cpu goes offline. Need to take
> > a closer look.
>
> I finally tracked it down. There were several ways to turn the box into
> a brick. Sigh !
>
> Can you please test the combo patch below ?
>
> The details are available from the for-2.6.23 branch of my hrt git repo:
>
> http://git.kernel.org/?p=linux/kernel/git/tglx/linux-2.6-hrt.git;a=shortlog;h=for-2.6.23
>

That patch fixes the resume-from-ram and suspend-to-ram regressions on the
Vaio.

I dropped the timekeeping.c hunks because they are an older version of
timekeeping-prevent-time-going-backwards-on-resume.patch which I already
had.

Is this good to go? Needs a bit of changelogging.


drivers/acpi/processor_core.c | 21 +++++++++++++++++++++
kernel/time/tick-broadcast.c | 24 ++++++++++++++++--------
kernel/time/tick-sched.c | 12 ++++++++++++
3 files changed, 49 insertions(+), 8 deletions(-)
diff -puN drivers/acpi/processor_core.c~cpu-hotplug-support-broken-in-2623-rc3 drivers/acpi/processor_core.c
--- a/drivers/acpi/processor_core.c~cpu-hotplug-support-broken-in-2623-rc3
+++ a/drivers/acpi/processor_core.c
@@ -724,6 +724,25 @@ static void acpi_processor_notify(acpi_h
return;
}

+static int acpi_cpu_soft_notify(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ unsigned int cpu = (unsigned long)hcpu;
+ struct acpi_processor *pr = processors[cpu];
+
+ if (action == CPU_ONLINE && pr) {
+ acpi_processor_ppc_has_changed(pr);
+ acpi_processor_cst_has_changed(pr);
+ acpi_processor_tstate_has_changed(pr);
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block acpi_cpu_notifier =
+{
+ .notifier_call = acpi_cpu_soft_notify,
+};
+
static int acpi_processor_add(struct acpi_device *device)
{
struct acpi_processor *pr = NULL;
@@ -987,6 +1006,7 @@ void acpi_processor_install_hotplug_noti
ACPI_UINT32_MAX,
processor_walk_namespace_cb, &action, NULL);
#endif
+ register_hotcpu_notifier(&acpi_cpu_notifier);
}

static
@@ -999,6 +1019,7 @@ void acpi_processor_uninstall_hotplug_no
ACPI_UINT32_MAX,
processor_walk_namespace_cb, &action, NULL);
#endif
+ unregister_hotcpu_notifier(&acpi_cpu_notifier);
}

/*
diff -puN kernel/time/tick-broadcast.c~cpu-hotplug-support-broken-in-2623-rc3 kernel/time/tick-broadcast.c
--- a/kernel/time/tick-broadcast.c~cpu-hotplug-support-broken-in-2623-rc3
+++ a/kernel/time/tick-broadcast.c
@@ -382,12 +382,23 @@ static int tick_broadcast_set_event(ktim

int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
{
+ int cpu = smp_processor_id();
+
+ /*
+ * If the CPU is marked for broadcast, enforce oneshot
+ * broadcast mode. The jinxed VAIO does not resume otherwise.
+ * No idea why it ends up in a lower C State during resume
+ * without notifying the clock events layer.
+ */
+ if (cpu_isset(cpu, tick_broadcast_mask))
+ cpu_set(cpu, tick_broadcast_oneshot_mask);
+
clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);

if(!cpus_empty(tick_broadcast_oneshot_mask))
tick_broadcast_set_event(ktime_get(), 1);

- return cpu_isset(smp_processor_id(), tick_broadcast_oneshot_mask);
+ return cpu_isset(cpu, tick_broadcast_oneshot_mask);
}

/*
@@ -549,20 +560,17 @@ void tick_broadcast_switch_to_oneshot(vo
*/
void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
{
- struct clock_event_device *bc;
unsigned long flags;
unsigned int cpu = *cpup;

spin_lock_irqsave(&tick_broadcast_lock, flags);

- bc = tick_broadcast_device.evtdev;
+ /*
+ * Clear the broadcast mask flag for the dead cpu, but do not
+ * stop the broadcast device!
+ */
cpu_clear(cpu, tick_broadcast_oneshot_mask);

- if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT) {
- if (bc && cpus_empty(tick_broadcast_oneshot_mask))
- clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
- }
-
spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

diff -puN kernel/time/tick-sched.c~cpu-hotplug-support-broken-in-2623-rc3 kernel/time/tick-sched.c
--- a/kernel/time/tick-sched.c~cpu-hotplug-support-broken-in-2623-rc3
+++ a/kernel/time/tick-sched.c
@@ -160,6 +160,18 @@ void tick_nohz_stop_sched_tick(void)
cpu = smp_processor_id();
ts = &per_cpu(tick_cpu_sched, cpu);

+ /*
+ * If this cpu is offline and it is the one which updates
+ * jiffies, then give up the assignment and let it be taken by
+ * the cpu which runs the tick timer next. If we don't drop
+ * this here the jiffies might be stale and do_timer() never
+ * invoked.
+ */
+ if (unlikely(!cpu_online(cpu))) {
+ if (cpu == tick_do_timer_cpu)
+ tick_do_timer_cpu = -1;
+ }
+
if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
goto end;

_
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