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>

diff --git a/arch/metag/kernel/smp.c b/arch/metag/kernel/smp.c
index 86fdda4a85c467c4da905025febb723a074520ad..b81351538c487d388717802ddba8f49022b07931 100644 (file)
--- 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;
 }