freezer: remove racy clear_freeze_flag() and set PF_NOFREEZE on dead tasks

clear_freeze_flag() in exit_mm() is racy.  Freezing can start
afterwards.  Remove it.  Skipping freezer for exiting task will be
properly implemented later.

Also, freezable() was testing exit_state directly to make system
freezer ignore dead tasks.  Let the exiting task set PF_NOFREEZE after
entering TASK_DEAD instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/kernel/power/process.c b/kernel/power/process.c
index fe2787207f00..23822dc14b6c 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -25,8 +25,7 @@
 static inline int freezable(struct task_struct * p)
 {
         if ((p == current) ||
-            (p->flags & PF_NOFREEZE) ||
-            (p->exit_state != 0))
+            (p->flags & PF_NOFREEZE))
                 return 0;
         return 1;
 }