From b68f8c769c688b182fc112f1e7c20fcb56a78eb7 Mon Sep 17 00:00:00 2001
From: Arturs Artamonovs <dos21h@gmail.com>
Date: Mon, 4 Dec 2023 22:37:17 +0000
Subject: Kernel thread creation process

---
 md/notes/kernel/create_thread.md | 139 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)

(limited to 'md/notes/kernel')

diff --git a/md/notes/kernel/create_thread.md b/md/notes/kernel/create_thread.md
index 87830b1..7f38c7c 100644
--- a/md/notes/kernel/create_thread.md
+++ b/md/notes/kernel/create_thread.md
@@ -3,6 +3,78 @@ keywords:kernel,linux,threads
 
 # Create threads
 
+## Starting point
+
+__Makefile__
+```Makefile
+obj-m += create_thread.o
+
+KDIR ?= /lib/modules/$(shell uname -r)/build
+
+all:
+	make -C $(KDIR) M=$(PWD) modules
+
+clean:
+	make -C $(KDIR) M=$(PWD) clean
+```
+
+__create_thread.c__
+```c
+#include <linux/module.h>  /* Needed by all modules */
+#include <linux/kernel.h>
+
+int create_thread_init( void )
+{
+	printk(KERN_DEBUG "Hello Thread!\n");
+	return 0;
+}
+
+void create_thread_exit( void )
+{
+	printk(KERN_DEBUG "Exit Thread!\n");
+}
+
+module_init( create_thread_init );
+module_exit( create_thread_exit );
+
+MODULE_LICENSE("GPL");
+```
+
+## Create empty thread
+
+Lets create kernel thread that will start and exit straight away
+
+
+```c
+#include <linux/delay.h>
+
+static struct task_struct *task;
+
+static int run_task(void *data) {
+	int i=0;
+	while(!kthread_should_stop())
+	{
+		pr_info("run task%d\n", i++);
+		msleep(1000);
+	} 
+	return 0; 
+}
+
+int create_thread_init( void ) {
+	...
+	task = kthread_create(run_task, NULL, "special task");
+	if(task) 
+	{
+		wake_up_process(task);
+	} else {
+		printk(KERN_ERR "Cannot create kthread\n"); 
+	}
+	...
+}
+
+```
+
+## Kernel threads states
 State of kernel thread  - include/linux/sched.h
 
 ```c
@@ -32,13 +104,80 @@ State of kernel thread  - include/linux/sched.h
 #define TASK_ANY			(TASK_STATE_MAX-1)
 ```
 
+
+## List of kernel thread functions used
+
+| Function name | Note |
+|---|---|
+|  |  |
+| wake_up_proces |  |
+| kthread_create |  |
+
+
+
+## Final result
+
+__create_thread.c__
+```c
+#include <linux/module.h>  /* Needed by all modules */
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/kthread.h>
+#include <linux/err.h>
+#include <linux/uaccess.h>
+#include <linux/cdev.h>
+#include <linux/delay.h>
+
+
+static struct task_struct *task;
+
+static int run_task(void *data) {
+	int i=0;
+	while(!kthread_should_stop())
+	{
+		pr_info("run task %d\n", i++);
+		msleep(1000);
+	} 
+	return 0; 
+}
+
+int create_thread_init( void )
+{
+	printk(KERN_DEBUG "Hello Thread!\n");
+
+	task = kthread_create(run_task, NULL, "special task");
+	if(task) 
+	{
+		wake_up_process(task);
+	} else {
+		printk(KERN_ERR "Cannot create kthread\n"); 
+	}
+
+	return 0;
+}
+
+void create_thread_exit( void )
+{
+	printk(KERN_DEBUG "Exit Thread!\n");
+}
+
+module_init( create_thread_init );
+module_exit( create_thread_exit );
+
+MODULE_LICENSE("GPL");
+```
+
 ## Links
 
 
 https://www.linuxtoday.com/blog/kernel-threads/  
 http://www.embeddedlinux.org.cn/EssentialLinuxDeviceDrivers/final/ch03lev1sec1.html  
+https://embetronicx.com/tutorials/linux/device-drivers/linux-device-drivers-tutorial-kernel-thread  
 https://elixir.bootlin.com/linux/v6.1.21/source/include/linux/sched.h  
 https://elixir.bootlin.com/linux/v6.1.21/source/kernel/sysctl.c  
+https://girishjoshi.io/post/creating-linux-kernel-threads/  
+https://tuxthink.blogspot.com/2011/02/kernel-thread-creation-1.html  
+https://elixir.bootlin.com/linux/v6.1.21/source/include/linux/kthread.h#L27  
 
 
 
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