Messages in this thread Patch in this message | | | From | Soren Brinkmann <> | Subject | [PATCH 1/2] tick: broadcast: Deny per-cpu clockevents from being broadcast sources | Date | Thu, 12 Sep 2013 09:50:39 -0700 |
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From: Stephen Boyd <sboyd@codeaurora.org>
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!).
Reported-by: Sören Brinkmann <soren.brinkmann@xilinx.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> --- kernel/time/tick-broadcast.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 218bcb5..d3539e5 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -77,6 +77,9 @@ static bool tick_check_broadcast_device(struct clock_event_device *curdev, !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) return false; + if (cpumask_equal(newdev->cpumask, cpumask_of(smp_processor_id()))) + return false; + return !curdev || newdev->rating > curdev->rating; } -- 1.8.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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