arm: use clear_tasks_mm_cpumask()

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@redhat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 7 deletions

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index b735521a4a54..2c7217d971db 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -109,7 +109,6 @@ 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);
@@ -139,12 +138,7 @@ int __cpu_disable(void)
         flush_cache_all();
         local_flush_tlb_all();
 
-        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;
 }