Commit 6acbfb96 authored May 16, 2014 by Lai Jiangshan Committed by Ingo Molnar May 22, 2014

sched: Fix hotplug vs. set_cpus_allowed_ptr()



Lai found that:

  WARNING: CPU: 1 PID: 13 at arch/x86/kernel/smp.c:124 native_smp_send_reschedule+0x2d/0x4b()
  ...
  migration_cpu_stop+0x1d/0x22

was caused by set_cpus_allowed_ptr() assuming that cpu_active_mask is
always a sub-set of cpu_online_mask.

This isn't true since 5fbd036b ("sched: Cleanup cpu_active madness").

So set active and online at the same time to avoid this particular
problem.

Fixes: 5fbd036b ("sched: Cleanup cpu_active madness")
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael wang <wangyun@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Link: http://lkml.kernel.org/r/53758B12.8060609@cn.fujitsu.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 4dac0b63

kernel/cpu.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -726,11 +726,13 @@ void set_cpu_present(unsigned int cpu, bool present)

		void set_cpu_online(unsigned int cpu, bool online)
		{
		if (online)
		if (online) {
		cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
		else
		cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
		} else {
		cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
		}
		}

		void set_cpu_active(unsigned int cpu, bool active)
		{

kernel/sched/core.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -5076,7 +5076,6 @@ static int sched_cpu_active(struct notifier_block *nfb,
		unsigned long action, void *hcpu)
		{
		switch (action & ~CPU_TASKS_FROZEN) {
		case CPU_STARTING:
		case CPU_DOWN_FAILED:
		set_cpu_active((long)hcpu, true);
		return NOTIFY_OK;