metag: 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() was introduced in v3.5-rc1 to fix this issue,
so let's use it for metag too.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>

1 files changed, 1 insertions, 7 deletions

diff --git a/arch/metag/kernel/smp.c b/arch/metag/kernel/smp.c
index 86fdda4a85c4..b81351538c48 100644
--- a/arch/metag/kernel/smp.c
+++ b/arch/metag/kernel/smp.c
@@ -276,7 +276,6 @@ static DECLARE_COMPLETION(cpu_killed);
 int __cpuexit __cpu_disable(void)
 {
         unsigned int cpu = smp_processor_id();
-        struct task_struct *p;
 
         /*
          * Take this CPU offline.  Once we clear this, we can't return,
@@ -296,12 +295,7 @@ int __cpuexit __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;
 }