tick: broadcast: Deny per-cpu clockevents from being broadcast sources

On most ARM systems the per-cpu clockevents are truly per-cpu in
the sense that they can't be controlled on any other CPU besides
the CPU that they interrupt. If one of these clockevents were to
become a broadcast source we will run into a lot of trouble
because the broadcast source is enabled on the first CPU to go
into deep idle (if that CPU suffers from FEAT_C3_STOP) and that
could be a different CPU than what the clockevent is interrupting
(or even worse the CPU that the clockevent interrupts could be
offline).

Theoretically it's possible to support per-cpu clockevents as the
broadcast source but so far we haven't needed this and supporting
it is rather complicated. Let's just deny the possibility for now
until this becomes a reality (let's hope it never does!).

Signed-off-by: Soren Brinkmann <[email protected]>
Signed-off-by: Daniel Lezcano <[email protected]>
Acked-by: Michal Simek <[email protected]>

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 218bcb565fed0f6e8f867b9e3e2264812d9797bf..9532690daaa9edff1fedd01066215ee43884a8a4 100644 (file)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -70,6 +70,7 @@ static bool tick_check_broadcast_device(struct clock_event_device *curdev,
                                        struct clock_event_device *newdev)
 {
        if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
+           (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
            (newdev->features & CLOCK_EVT_FEAT_C3STOP))
                return false;