Re: [PATCH v2 3/4] tick: broadcast: Deny per-cpu clockevents from being broadcast sources
From: Daniel Lezcano <hidden>
Date: 2013-09-25 15:11:52
Also in:
linux-arm-kernel, lkml
On 09/18/2013 08:48 PM, Soren Brinkmann wrote:
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 <redacted>
Acked-by: Daniel Lezcano <redacted>
quoted hunk ↗ jump to hunk
--- 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;
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