[RFC][PATCH 3/6][v3] Define/set SIGNAL_UNKILLABLE_FROM_NS

[Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Date: Sat, 20 Dec 2008 12:27:47 -0800
Subject: [RFC][PATCH 3/6][v3] Define/set SIGNAL_UNKILLABLE_FROM_NS

Define and set the SIGNAL_UNKILLABLE_FROM_NS flags for container-inits.
This flag will be used in follow-on patches to ignore/drop fatal sigals
to container-init from within the container but process the signals from
an ancestor container.

Based on discussions on earlier version of this patchset:
	http://lkml.org/lkml/2008/11/25/462

Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
---
 include/linux/sched.h |    3 +++
 kernel/fork.c         |    2 ++
 2 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 96c6703..19c4311 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -604,6 +604,9 @@ struct signal_struct {
 
 #define SIGNAL_UNKILLABLE	0x00000040 /* for init: ignore fatal signals */
 
+/* for container-init: ignore fatal signals from within container */
+#define SIGNAL_UNKILLABLE_FROM_NS 0x00000080
+
 /* If true, all threads except ->group_exit_task have pending SIGKILL */
 static inline int signal_group_exit(const struct signal_struct *sig)
 {
diff --git a/kernel/fork.c b/kernel/fork.c
index dba2d3f..0a959f5 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -812,6 +812,8 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 	atomic_set(&sig->live, 1);
 	init_waitqueue_head(&sig->wait_chldexit);
 	sig->flags = 0;
+	if (clone_flags & CLONE_NEWPID)
+		sig->flags |= SIGNAL_UNKILLABLE_FROM_NS;
 	sig->group_exit_code = 0;
 	sig->group_exit_task = NULL;
 	sig->group_stop_count = 0;
-- 
1.5.2.5