Name: __kernel_thread
Author: Rusty Russell
Status: Experimental

D: kernel_thread creates and starts a new kernel thread.  Introduce
D: __kernel_thread and start_kernel_thread which split this into to
D: copy_process() part and the actual starting part.  This is useful
D: for more sophisticated thread creation, such as required for hotplug
D: cpus creating new idle threads, and two-stage CPU bringup.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .6154-linux-2.5.74-bk7/arch/i386/kernel/process.c .6154-linux-2.5.74-bk7.updated/arch/i386/kernel/process.c
--- .6154-linux-2.5.74-bk7/arch/i386/kernel/process.c	2003-06-23 10:52:42.000000000 +1000
+++ .6154-linux-2.5.74-bk7.updated/arch/i386/kernel/process.c	2003-07-10 13:01:06.000000000 +1000
@@ -210,7 +210,9 @@ __asm__(".align 4\n"
 /*
  * Create a kernel thread
  */
-int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
+struct task_struct *__kernel_thread(int (*fn)(void *),
+				    void *arg,
+				    unsigned long flags)
 {
 	struct pt_regs regs;
 
@@ -227,7 +229,8 @@ int kernel_thread(int (*fn)(void *), voi
 	regs.eflags = 0x286;
 
 	/* Ok, create the new process.. */
-	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
+	return copy_process(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0,
+			    NULL, NULL);
 }
 
 /*
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .6154-linux-2.5.74-bk7/include/asm-i386/processor.h .6154-linux-2.5.74-bk7.updated/include/asm-i386/processor.h
--- .6154-linux-2.5.74-bk7/include/asm-i386/processor.h	2003-06-23 10:52:55.000000000 +1000
+++ .6154-linux-2.5.74-bk7.updated/include/asm-i386/processor.h	2003-07-10 14:46:12.000000000 +1000
@@ -463,9 +463,10 @@ extern void release_thread(struct task_s
 extern void prepare_to_copy(struct task_struct *tsk);
 
 /*
- * create a kernel thread without removing it from tasklists
+ * create a kernel thread without removing it from tasklists, don't start it.
  */
-extern int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags);
+extern struct task_struct *__kernel_thread(int (*fn)(void *),
+					   void *arg, unsigned long flags);
 
 extern unsigned long thread_saved_pc(struct task_struct *tsk);
 void show_trace(struct task_struct *task, unsigned long *stack);
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .6154-linux-2.5.74-bk7/kernel/fork.c .6154-linux-2.5.74-bk7.updated/kernel/fork.c
--- .6154-linux-2.5.74-bk7/kernel/fork.c	2003-07-10 10:55:48.000000000 +1000
+++ .6154-linux-2.5.74-bk7.updated/kernel/fork.c	2003-07-10 13:05:57.000000000 +1000
@@ -1135,6 +1135,39 @@ long do_fork(unsigned long clone_flags,
 	return pid;
 }
 
+void start_kernel_thread(struct task_struct *p, int vforked)
+{
+	struct completion vfork;
+
+	if (vforked) {
+		p->vfork_done = &vfork;
+		init_completion(&vfork);
+	}
+
+	wake_up_forked_process(p);
+	++total_forks;
+
+	if (vforked)
+		wait_for_completion(&vfork);
+}
+
+int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
+{
+	struct task_struct *p;
+	int pid;
+
+	p = __kernel_thread(fn, arg, flags);
+	if (IS_ERR(p))
+		return PTR_ERR(p);
+
+	/* Grab pid before it's woken: it could exit immediately. */
+	pid = p->pid;
+
+	start_kernel_thread(p, flags & CLONE_VFORK);
+	return pid;
+}
+
+
 /* SLAB cache for signal_struct structures (tsk->signal) */
 kmem_cache_t *signal_cachep;