[PATCH RFC 06/13] core: Add rwlock_t task_list::kin_lock

[Kirill Tkhai <ktkhai@odin.com>]

Add a new primitive for synchronization between relatives.
It will be used in next/further patches.

Signed-off-by: Kirill Tkhai <ktkhai@odin.com>
---
 include/linux/init_task.h |    1 +
 include/linux/sched.h     |    1 +
 kernel/fork.c             |    1 +
 3 files changed, 3 insertions(+)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index bb9b075..919243a 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -218,6 +218,7 @@ extern struct task_group root_task_group;
 	.parent		= &tsk,						\
 	.children	= LIST_HEAD_INIT(tsk.children),			\
 	.sibling	= LIST_HEAD_INIT(tsk.sibling),			\
+	.kin_lock	= __RW_LOCK_UNLOCKED(tsk.kin_lock),		\
 	.group_leader	= &tsk,						\
 	RCU_POINTER_INITIALIZER(real_cred, &init_cred),			\
 	RCU_POINTER_INITIALIZER(cred, &init_cred),			\
diff --git a/include/linux/sched.h b/include/linux/sched.h
index af0eeba..58dc09f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1477,6 +1477,7 @@ struct task_struct {
 	struct list_head children;	/* list of my children */
 	struct list_head sibling;	/* linkage in my parent's children list */
 	struct task_struct *group_leader;	/* threadgroup leader */
+	rwlock_t kin_lock;
 
 	/*
 	 * ptraced is the list of tasks this task is using ptrace on.
diff --git a/kernel/fork.c b/kernel/fork.c
index 66e31eb..ee389ba 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1330,6 +1330,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	p->flags |= PF_FORKNOEXEC;
 	INIT_LIST_HEAD(&p->children);
 	INIT_LIST_HEAD(&p->sibling);
+	rwlock_init(&p->kin_lock);
 	rcu_copy_process(p);
 	p->vfork_done = NULL;
 	spin_lock_init(&p->alloc_lock);