From 6145372cf2b6fbfc1cf83905a23e991e4d0d3144 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 23 Mar 2012 15:01:54 -0700
Subject: [PATCH] --- yaml --- r: 295151 b: refs/heads/master c:
 ebec18a6d3aa1e7d84aab16225e87fd25170ec2b h: refs/heads/master i:   295149:
 eb9d4b80f8bd100d63f2008a2d9cd5fbd7b12637   295147:
 ad96cf275274017c69def88cd7b6f037860a63b0   295143:
 10f8f60a1512ece58b1360d466edaddbc860ce4a   295135:
 bf09ff03abbf8aba35d3a982f316b04248db34be v: v3

---
 [refs]                      |  2 +-
 trunk/include/linux/prctl.h |  3 +++
 trunk/include/linux/sched.h | 12 ++++++++++++
 trunk/kernel/exit.c         | 33 ++++++++++++++++++++++++++++-----
 trunk/kernel/fork.c         |  3 +++
 trunk/kernel/sys.c          |  8 ++++++++
 6 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/[refs] b/[refs]
index 2d66c568aa3a..4114dfaf9123 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 953326cb60c1dff1bd3458d6468d16d75f2bcd61
+refs/heads/master: ebec18a6d3aa1e7d84aab16225e87fd25170ec2b
diff --git a/trunk/include/linux/prctl.h b/trunk/include/linux/prctl.h
index a0413ac3abe8..e0cfec2490aa 100644
--- a/trunk/include/linux/prctl.h
+++ b/trunk/include/linux/prctl.h
@@ -121,4 +121,7 @@
 #define PR_SET_PTRACER 0x59616d61
 # define PR_SET_PTRACER_ANY ((unsigned long)-1)
 
+#define PR_SET_CHILD_SUBREAPER 36
+#define PR_GET_CHILD_SUBREAPER 37
+
 #endif /* _LINUX_PRCTL_H */
diff --git a/trunk/include/linux/sched.h b/trunk/include/linux/sched.h
index 0c147a4260a5..0c3854b0d4b1 100644
--- a/trunk/include/linux/sched.h
+++ b/trunk/include/linux/sched.h
@@ -553,6 +553,18 @@ struct signal_struct {
 	int			group_stop_count;
 	unsigned int		flags; /* see SIGNAL_* flags below */
 
+	/*
+	 * PR_SET_CHILD_SUBREAPER marks a process, like a service
+	 * manager, to re-parent orphan (double-forking) child processes
+	 * to this process instead of 'init'. The service manager is
+	 * able to receive SIGCHLD signals and is able to investigate
+	 * the process until it calls wait(). All children of this
+	 * process will inherit a flag if they should look for a
+	 * child_subreaper process at exit.
+	 */
+	unsigned int		is_child_subreaper:1;
+	unsigned int		has_child_subreaper:1;
+
 	/* POSIX.1b Interval Timers */
 	struct list_head posix_timers;
 
diff --git a/trunk/kernel/exit.c b/trunk/kernel/exit.c
index 16b07bfac224..456329fd4ea3 100644
--- a/trunk/kernel/exit.c
+++ b/trunk/kernel/exit.c
@@ -687,11 +687,11 @@ static void exit_mm(struct task_struct * tsk)
 }
 
 /*
- * When we die, we re-parent all our children.
- * Try to give them to another thread in our thread
- * group, and if no such member exists, give it to
- * the child reaper process (ie "init") in our pid
- * space.
+ * When we die, we re-parent all our children, and try to:
+ * 1. give them to another thread in our thread group, if such a member exists
+ * 2. give it to the first ancestor process which prctl'd itself as a
+ *    child_subreaper for its children (like a service manager)
+ * 3. give it to the init process (PID 1) in our pid namespace
  */
 static struct task_struct *find_new_reaper(struct task_struct *father)
 	__releases(&tasklist_lock)
@@ -722,6 +722,29 @@ static struct task_struct *find_new_reaper(struct task_struct *father)
 		 * forget_original_parent() must move them somewhere.
 		 */
 		pid_ns->child_reaper = init_pid_ns.child_reaper;
+	} else if (father->signal->has_child_subreaper) {
+		struct task_struct *reaper;
+
+		/*
+		 * Find the first ancestor marked as child_subreaper.
+		 * Note that the code below checks same_thread_group(reaper,
+		 * pid_ns->child_reaper).  This is what we need to DTRT in a
+		 * PID namespace. However we still need the check above, see
+		 * http://marc.info/?l=linux-kernel&m=131385460420380
+		 */
+		for (reaper = father->real_parent;
+		     reaper != &init_task;
+		     reaper = reaper->real_parent) {
+			if (same_thread_group(reaper, pid_ns->child_reaper))
+				break;
+			if (!reaper->signal->is_child_subreaper)
+				continue;
+			thread = reaper;
+			do {
+				if (!(thread->flags & PF_EXITING))
+					return reaper;
+			} while_each_thread(reaper, thread);
+		}
 	}
 
 	return pid_ns->child_reaper;
diff --git a/trunk/kernel/fork.c b/trunk/kernel/fork.c
index 37674ec55cde..b9372a0bff18 100644
--- a/trunk/kernel/fork.c
+++ b/trunk/kernel/fork.c
@@ -1051,6 +1051,9 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 	sig->oom_score_adj = current->signal->oom_score_adj;
 	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
 
+	sig->has_child_subreaper = current->signal->has_child_subreaper ||
+				   current->signal->is_child_subreaper;
+
 	mutex_init(&sig->cred_guard_mutex);
 
 	return 0;
diff --git a/trunk/kernel/sys.c b/trunk/kernel/sys.c
index 888d227fd195..9eb7fcab8df6 100644
--- a/trunk/kernel/sys.c
+++ b/trunk/kernel/sys.c
@@ -1962,6 +1962,14 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 		case PR_SET_MM:
 			error = prctl_set_mm(arg2, arg3, arg4, arg5);
 			break;
+		case PR_SET_CHILD_SUBREAPER:
+			me->signal->is_child_subreaper = !!arg2;
+			error = 0;
+			break;
+		case PR_GET_CHILD_SUBREAPER:
+			error = put_user(me->signal->is_child_subreaper,
+					 (int __user *) arg2);
+			break;
 		default:
 			error = -EINVAL;
 			break;