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Date: Sat, 15 Sep 2007 11:49:41 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Pavel Machek <pavel@....cz>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>,
Jeff Chua <jeff.chua.linux@...il.com>, rusty@...tycorp.com.au,
vatsa@...ibm.com, zwane@....linux.org.uk,
kernel list <linux-kernel@...r.kernel.org>,
Len Brown <lenb@...nel.org>
Subject: Re: cpu hotplug support broken in 2.6.23-rc3
Pavel,
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
Thanks,
tglx
Index: linux-2.6/kernel/time/timekeeping.c
===================================================================
--- linux-2.6.orig/kernel/time/timekeeping.c 2007-09-15 11:42:09.000000000 +0200
+++ linux-2.6/kernel/time/timekeeping.c 2007-09-15 11:43:03.000000000 +0200
@@ -217,6 +217,7 @@ static void change_clocksource(void)
}
#else
static inline void change_clocksource(void) { }
+static inline s64 __get_nsec_offset(void) { return 0; }
#endif
/**
@@ -280,6 +281,8 @@ void __init timekeeping_init(void)
static int timekeeping_suspended;
/* time in seconds when suspend began */
static unsigned long timekeeping_suspend_time;
+/* xtime offset when we went into suspend */
+static s64 timekeeping_suspend_nsecs;
/**
* timekeeping_resume - Resumes the generic timekeeping subsystem.
@@ -305,6 +308,8 @@ static int timekeeping_resume(struct sys
wall_to_monotonic.tv_sec -= sleep_length;
total_sleep_time += sleep_length;
}
+ /* Make sure that we have the correct xtime reference */
+ timespec_add_ns(&xtime, timekeeping_suspend_nsecs);
/* re-base the last cycle value */
clock->cycle_last = clocksource_read(clock);
clock->error = 0;
@@ -325,9 +330,12 @@ static int timekeeping_suspend(struct sy
{
unsigned long flags;
+ timekeeping_suspend_time = read_persistent_clock();
+
write_seqlock_irqsave(&xtime_lock, flags);
+ /* Get the current xtime offset */
+ timekeeping_suspend_nsecs = __get_nsec_offset();
timekeeping_suspended = 1;
- timekeeping_suspend_time = read_persistent_clock();
write_sequnlock_irqrestore(&xtime_lock, flags);
clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
Index: linux-2.6/drivers/acpi/processor_core.c
===================================================================
--- linux-2.6.orig/drivers/acpi/processor_core.c 2007-09-15 11:42:09.000000000 +0200
+++ linux-2.6/drivers/acpi/processor_core.c 2007-09-15 11:43:03.000000000 +0200
@@ -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);
}
/*
Index: linux-2.6/kernel/time/tick-broadcast.c
===================================================================
--- linux-2.6.orig/kernel/time/tick-broadcast.c 2007-09-15 11:42:09.000000000 +0200
+++ linux-2.6/kernel/time/tick-broadcast.c 2007-09-15 11:43:03.000000000 +0200
@@ -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);
}
Index: linux-2.6/kernel/time/tick-sched.c
===================================================================
--- linux-2.6.orig/kernel/time/tick-sched.c 2007-09-15 11:42:09.000000000 +0200
+++ linux-2.6/kernel/time/tick-sched.c 2007-09-15 11:43:41.000000000 +0200
@@ -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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