2.6.25-stable review patch. If anyone has any objections, please let us
know.
------------------
From: Thomas Gleixner <tglx@linutronix.de>
commit 7300711e8c6824fcfbd42a126980ff50439d8dd0 upstream
Until the C1E patches arrived there where no users of periodic broadcast
before switching to oneshot mode. Now we need to trigger a possible
waiter for a periodic broadcast when switching to oneshot mode.
Otherwise we can starve them for ever.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
kernel/time/tick-broadcast.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -490,6 +490,18 @@ static void tick_broadcast_clear_oneshot
cpu_clear(cpu, tick_broadcast_oneshot_mask);
}
+static void tick_broadcast_init_next_event(cpumask_t *mask, ktime_t expires)
+{
+ struct tick_device *td;
+ int cpu;
+
+ for_each_cpu_mask(cpu, *mask) {
+ td = &per_cpu(tick_cpu_device, cpu);
+ if (td->evtdev)
+ td->evtdev->next_event = expires;
+ }
+}
+
/**
* tick_broadcast_setup_oneshot - setup the broadcast device
*/
@@ -497,9 +509,32 @@ void tick_broadcast_setup_oneshot(struct
{
/* Set it up only once ! */
if (bc->event_handler != tick_handle_oneshot_broadcast) {
+ int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
+ int cpu = smp_processor_id();
+ cpumask_t mask;
+
bc->event_handler = tick_handle_oneshot_broadcast;
clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
- bc->next_event.tv64 = KTIME_MAX;
+
+ /* Take the do_timer update */
+ tick_do_timer_cpu = cpu;
+
+ /*
+ * We must be careful here. There might be other CPUs
+ * waiting for periodic broadcast. We need to set the
+ * oneshot_mask bits for those and program the
+ * broadcast device to fire.
+ */
+ mask = tick_broadcast_mask;
+ cpu_clear(cpu, mask);
+ cpus_or(tick_broadcast_oneshot_mask,
+ tick_broadcast_oneshot_mask, mask);
+
+ if (was_periodic && !cpus_empty(mask)) {
+ tick_broadcast_init_next_event(&mask, tick_next_period);
+ tick_broadcast_set_event(tick_next_period, 1);
+ } else
+ bc->next_event.tv64 = KTIME_MAX;
}
}
--
--
