Commit 8eb23126 authored Jul 07, 2015 by Thomas Gleixner

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

parent 7c4a976c

kernel/time/tick-broadcast.c

+15 −1

Original line number	Diff line number	Diff line
		@@ -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)) {

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