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-rw-r--r--kernel/exit.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 303bed2..97dd317 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1049,6 +1049,22 @@ NORET_TYPE void do_exit(long code)
preempt_disable();
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;
schedule();