Merge commit 'v3.3-rc4'

1 files changed, 16 insertions, 0 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 294b1709170d..4b4042f9bc6a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1038,6 +1038,22 @@ void do_exit(long code)
         if (tsk->nr_dirtied)
                 __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
         exit_rcu();
+
+        /*
+         * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
+         * when the following two conditions become true.
+         *   - There is race condition of mmap_sem (It is acquired by
+         *     exit_mm()), and
+         *   - SMI occurs before setting TASK_RUNINNG.
+         *     (or hypervisor of virtual machine switches to other guest)
+         *  As a result, we may become TASK_RUNNING after becoming TASK_DEAD
+         *
+         * To avoid it, we have to wait for releasing tsk->pi_lock which
+         * is held by try_to_wake_up()
+         */
+        smp_mb();
+        raw_spin_unlock_wait(&tsk->pi_lock);
+
         /* causes final put_task_struct in finish_task_switch(). */
         tsk->state = TASK_DEAD;
         tsk->flags |= PF_NOFREEZE;      /* tell freezer to ignore us */