[PATCH 2/9] arm: Use clear_tasks_mm_cpumask()

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Checking for process->mm is not enough because process' main
thread may exit or detach its mm via use_mm(), but other threads
may still have a valid mm.

To fix this we would need to use find_lock_task_mm(), which would
walk up all threads and returns an appropriate task (with task
lock held).

clear_tasks_mm_cpumask() has this issue fixed, so let's use it.

Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
 arch/arm/kernel/smp.c |    8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index addbbe8..e824ee4 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -130,7 +130,6 @@ static void percpu_timer_stop(void);
 int __cpu_disable(void)
 	unsigned int cpu = smp_processor_id();
-	struct task_struct *p;
 	int ret;
 	ret = platform_cpu_disable(cpu);
@@ -160,12 +159,7 @@ int __cpu_disable(void)
-	read_lock(&tasklist_lock);
-	for_each_process(p) {
-		if (p->mm)
-			cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
-	}
-	read_unlock(&tasklist_lock);
+	clear_tasks_mm_cpumask(cpu);
 	return 0;

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