From a272dcca1802a7e265a56e60b0d0a6715b0a8ac2 Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Thu, 11 Jul 2013 07:00:59 -0700 Subject: [PATCH] tick: broadcast: Check broadcast mode on CPU hotplug On ARM systems the dummy clockevent is registered with the cpu hotplug notifier chain before any other per-cpu clockevent. This has the side-effect of causing the dummy clockevent to be registered first in every hotplug sequence. Because the dummy is first, we'll try to turn the broadcast source on but the code in tick_device_uses_broadcast() assumes the broadcast source is in periodic mode and calls tick_broadcast_start_periodic() unconditionally. On boot this isn't a problem because we typically haven't switched into oneshot mode yet (if at all). During hotplug, if the broadcast source isn't in periodic mode we'll replace the broadcast oneshot handler with the broadcast periodic handler and start emulating oneshot mode when we shouldn't. Due to the way the broadcast oneshot handler programs the next_event it's possible for it to contain KTIME_MAX and cause us to hang the system when the periodic handler tries to program the next tick. Fix this by using the appropriate function to start the broadcast source. Reported-by: Stephen Warren Tested-by: Stephen Warren Signed-off-by: Stephen Boyd Cc: Mark Rutland Cc: Marc Zyngier Cc: ARM kernel mailing list Cc: John Stultz Cc: Joseph Lo Link: http://lkml.kernel.org/r/20130711140059.GA27430@codeaurora.org Signed-off-by: Thomas Gleixner --- kernel/time/tick-broadcast.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 6d3f91631de6..218bcb565fed 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -157,7 +157,10 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu) dev->event_handler = tick_handle_periodic; tick_device_setup_broadcast_func(dev); cpumask_set_cpu(cpu, tick_broadcast_mask); - tick_broadcast_start_periodic(bc); + if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) + tick_broadcast_start_periodic(bc); + else + tick_broadcast_setup_oneshot(bc); ret = 1; } else { /* -- 2.20.1