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Subject[tip:sched/core] sched: Fix hotplug vs set_cpus_allowed_ptr()
Commit-ID:  b961b5eea6f90e269bfdec7cd0dac98b008ae817
Gitweb: http://git.kernel.org/tip/b961b5eea6f90e269bfdec7cd0dac98b008ae817
Author: Lai Jiangshan <laijs@cn.fujitsu.com>
AuthorDate: Fri, 16 May 2014 11:50:42 +0800
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 19 May 2014 21:47:34 +0900

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 5fbd036b552f ("sched: Cleanup cpu_active
madness").

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

Fixes: 5fbd036b552f ("sched: Cleanup cpu_active madness")
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/53758B12.8060609@cn.fujitsu.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/cpu.c | 6 ++++--
kernel/sched/core.c | 1 -
2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index a9e710e..247979a 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -726,10 +726,12 @@ 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)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 44e00ab..86f3890 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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;

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