From mboxrd@z Thu Jan 1 00:00:00 1970 From: soren.brinkmann@xilinx.com (Soren Brinkmann) Date: Thu, 12 Sep 2013 09:50:39 -0700 Subject: [PATCH 1/2] tick: broadcast: Deny per-cpu clockevents from being broadcast sources In-Reply-To: <1379004640-15117-1-git-send-email-soren.brinkmann@xilinx.com> References: <1379004640-15117-1-git-send-email-soren.brinkmann@xilinx.com> Message-ID: <1379004640-15117-2-git-send-email-soren.brinkmann@xilinx.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Stephen Boyd 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: S?ren Brinkmann Signed-off-by: Stephen Boyd --- 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