tick/broadcast: Prevent hrtimer recursion

The hrtimer based broadcast vehicle can cause a hrtimer recursion
which went unnoticed until we changed the hrtimer expiry code to keep
track of the currently running timer.

local_timer_interrupt()
  local_handler()
    hrtimer_interrupt()
      expire_hrtimers()
        broadcast_hrtimer()
	  send_ipis()
	  local_handler()
	    hrtimer_interrupt()
	     ....

Solution is simple: Prevent the local handler call from the broadcast
code when the broadcast 'device' is hrtimer based.

[ Split out from a larger combo patch ]

Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Suzuki Poulose <Suzuki.Poulose@arm.com>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
Cc: Catalin Marinas <Catalin.Marinas@arm.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1507070929360.3916@nanos

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index d39f32cdd1b59cca97066430442e3aa054cc9eed..a76204089f78aae77eb66d81c5093192774bd8f4 100644 (file)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -265,8 +265,22 @@ static bool tick_do_broadcast(struct cpumask *mask)
         * Check, if the current cpu is in the mask
         */
        if (cpumask_test_cpu(cpu, mask)) {
+               struct clock_event_device *bc = tick_broadcast_device.evtdev;
+
                cpumask_clear_cpu(cpu, mask);
-               local = true;
+               /*
+                * We only run the local handler, if the broadcast
+                * device is not hrtimer based. Otherwise we run into
+                * a hrtimer recursion.
+                *
+                * local timer_interrupt()
+                *   local_handler()
+                *     expire_hrtimers()
+                *       bc_handler()
+                *         local_handler()
+                *           expire_hrtimers()
+                */
+               local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
        }
 
        if (!cpumask_empty(mask)) {