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sched: _cpu_down(): Don't play with current->cpus_allowed

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_cpu_down() changes the current task's affinity and then recovers it at
the end. The problems are well known: we can't restore old_allowed if it
was bound to the now-dead-cpu, and we can race with the userspace which
can change cpu-affinity during unplug.

_cpu_down() should not play with current->cpus_allowed at all. Instead,
take_cpu_down() can migrate the caller of _cpu_down() after __cpu_disable()
removes the dying cpu from cpu_online_mask.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100315091023.GA9148@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Oleg Nesterov
2010-03-15 10:10:23 +01:00
committed by Ingo Molnar
parent 30da688ef6
commit 6a1bdc1b57
3 changed files with 8 additions and 13 deletions
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2
kernel/sched.c
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@@ -5442,7 +5442,7 @@ static int migration_thread(void *data)
/*
* Figure out where task on dead CPU should go, use force if necessary.
*/
static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
{
struct rq *rq = cpu_rq(dead_cpu);
int needs_cpu, uninitialized_var(dest_cpu);