From: w@1wt.eu (Willy Tarreau) Date: Tue, 04 Jun 2013 19:21:34 +0200 Subject: [ 004/184] clockevents: Dont allow dummy broadcast timers In-Reply-To: <58df134a4b98edf5b0073e2e1e988fe6@local> Message-ID: <20130604172130.471073557@1wt.eu> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Mark Rutland commit a7dc19b8652c862d5b7c4d2339bd3c428bd29c4a upstream. Currently tick_check_broadcast_device doesn't reject clock_event_devices with CLOCK_EVT_FEAT_DUMMY, and may select them in preference to real hardware if they have a higher rating value. In this situation, the dummy timer is responsible for broadcasting to itself, and the core clockevents code may attempt to call non-existent callbacks for programming the dummy, eventually leading to a panic. This patch makes tick_check_broadcast_device always reject dummy timers, preventing this problem. Signed-off-by: Mark Rutland Cc: linux-arm-kernel at lists.infradead.org Cc: Jon Medhurst (Tixy) Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman Signed-off-by: Willy Tarreau --- kernel/time/tick-broadcast.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 57b953f..67fe3d9 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -67,7 +67,8 @@ static void tick_broadcast_start_periodic(struct clock_event_device *bc) */ int tick_check_broadcast_device(struct clock_event_device *dev) { - if ((tick_broadcast_device.evtdev && + if ((dev->features & CLOCK_EVT_FEAT_DUMMY) || + (tick_broadcast_device.evtdev && tick_broadcast_device.evtdev->rating >= dev->rating) || (dev->features & CLOCK_EVT_FEAT_C3STOP)) return 0; -- 1.7.12.2.21.g234cd45.dirty