From 245a34962661cd2ce7b4dd6c4aa65d870a589c50 Mon Sep 17 00:00:00 2001 From: Soren Brinkmann Date: Wed, 18 Sep 2013 11:48:37 -0700 Subject: [PATCH] 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 Signed-off-by: Daniel Lezcano Acked-by: Michal Simek --- kernel/time/tick-broadcast.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 218bcb5..9532690 100644 --- 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; -- 2.7.4