Commit f6c3f168 authored Sep 13, 2010 by Suresh Siddha Committed by Ingo Molnar Sep 21, 2010

sched: Fix nohz balance kick



There's a situation where the nohz balancer will try to wake itself:

cpu-x is idle which is also ilb_cpu
got a scheduler tick during idle
and the nohz_kick_needed() in trigger_load_balance() checks for
rq_x->nr_running which might not be zero (because of someone waking a
task on this rq etc) and this leads to the situation of the cpu-x
sending a kick to itself.

And this can cause a lockup.

Avoid this by not marking ourself eligible for kicking.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1284400941.2684.19.camel@sbsiddha-MOBL3.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent e75e863d

kernel/sched_fair.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -3630,7 +3630,7 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu)
		if (time_before(now, nohz.next_balance))
		return 0;

		if (!rq->nr_running)
		if (rq->idle_at_tick)
		return 0;

		first_pick_cpu = atomic_read(&nohz.first_pick_cpu);

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