Merge tag 'fbdev-fixes-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tomba...

[cascardo/linux.git] / kernel / cpu.c

diff --git a/kernel/cpu.c b/kernel/cpu.c
index a343bde..81e2a38 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -274,21 +274,28 @@ void clear_tasks_mm_cpumask(int cpu)
        rcu_read_unlock();
 }
 
-static inline void check_for_tasks(int cpu)
+static inline void check_for_tasks(int dead_cpu)
 {
-       struct task_struct *p;
-       cputime_t utime, stime;
+       struct task_struct *g, *p;
 
-       write_lock_irq(&tasklist_lock);
-       for_each_process(p) {
-               task_cputime(p, &utime, &stime);
-               if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
-                   (utime || stime))
-                       pr_warn("Task %s (pid = %d) is on cpu %d (state = %ld, flags = %x)\n",
-                               p->comm, task_pid_nr(p), cpu,
-                               p->state, p->flags);
-       }
-       write_unlock_irq(&tasklist_lock);
+       read_lock_irq(&tasklist_lock);
+       do_each_thread(g, p) {
+               if (!p->on_rq)
+                       continue;
+               /*
+                * We do the check with unlocked task_rq(p)->lock.
+                * Order the reading to do not warn about a task,
+                * which was running on this cpu in the past, and
+                * it's just been woken on another cpu.
+                */
+               rmb();
+               if (task_cpu(p) != dead_cpu)
+                       continue;
+
+               pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
+                       p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
+       } while_each_thread(g, p);
+       read_unlock_irq(&tasklist_lock);
 }
 
 struct take_cpu_down_param {