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Groups > linux.kernel > #1178780

[tip:timers/urgent] tick/broadcast: Prevent hrtimer recursion

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Commit-ID:  8eb231261fdd20768db23863d00ef277de4b0543
Gitweb:     http://git.kernel.org/tip/8eb231261fdd20768db23863d00ef277de4b0543
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Tue, 7 Jul 2015 14:11:00 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 7 Jul 2015 18:46:47 +0200

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
---
 kernel/time/tick-broadcast.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index d39f32c..a762040 100644
--- 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)) {
--
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[tip:timers/urgent] tick/broadcast: Prevent hrtimer recursion tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2015-07-07 19:20 +0200

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