Schedule Work
=============

.. panels::
        :container: container pb-4
        :column: col-lg-12 p-2
        :card: shadow

        Topics in this section,

                * :ref:`Version Info <schedule_workqueue_0>`

                * :ref:`Learnings in this program <schedule_workqueue_1>`
                
                * :ref:`Explanation of Workqueue APIs <schedule_workqueue_2>`

                        * :ref:`INIT_WORK <schedule_workqueue_3>`
                        
                        * :ref:`schedule_work_on <schedule_workqueue_4>`

                        * :ref:`cancel_work_sync <schedule_workqueue_5>`

                        * :ref:`INIT_DELAYED_WORK <schedule_workqueue_6>`
                        
                        * :ref:`schedule_delayed_work_on <schedule_workqueue_7>`

                        * :ref:`cancel_delayed_work_sync <schedule_workqueue_8>`
                         
                        * :ref:`work_on_cpu <schedule_workqueue_9>`    

                        * :ref:`work_on_cpu_safe <schedule_workqueue_10>`

                * :ref:`Example 1 : Scheduling the workqueue <schedule_workqueue_11>`

                        * :ref:`List of headers <schedule_workqueue_12>`
                
                        * :ref:`Module macros <schedule_workqueue_13>`

                        * :ref:`Initialize work <schedule_workqueue_14>`

                        * :ref:`Workqueue Handler Function <schedule_workqueue_15>`

                        * :ref:`Queue Start Function <schedule_workqueue_16>`

                        * :ref:`Queue Init Function <schedule_workqueue_17>`

                        * :ref:`Queue Stop Function <schedule_workqueue_18>`

                        * :ref:`Queue Exit Function <schedule_workqueue_19>`

                        * :ref:`Driver entry points <schedule_workqueue_20>`

                        * :ref:`See the full program below <schedule_workqueue_21>`

                        * :ref:`Makefile <schedule_workqueue_22>`

                        * :ref:`Compile and Load <schedule_workqueue_23>`

                * :ref:`Example 2 : Scheduling the workqueue <schedule_workqueue_24>`

                        * :ref:`List of headers <schedule_workqueue_25>`
                
                        * :ref:`Module macros <schedule_workqueue_26>`

                        * :ref:`Initialize work <schedule_workqueue_27>`

                        * :ref:`Workqueue Handler Function <schedule_workqueue_28>`

                        * :ref:`Queue Start Function <schedule_workqueue_29>`

                        * :ref:`Queue Init Function <schedule_workqueue_30>`

                        * :ref:`Queue Stop Function <schedule_workqueue_31>`

                        * :ref:`Queue Exit Function <schedule_workqueue_32>`

                        * :ref:`Driver entry points <schedule_workqueue_33>`

                        * :ref:`See the full program below <schedule_workqueue_34>`

                        * :ref:`Makefile <schedule_workqueue_35>`

                        * :ref:`Compile and Load <schedule_workqueue_36>`
                
                * :ref:`Example 3 : Scheduling the workqueue <schedule_workqueue_37>`

                        * :ref:`List of headers <schedule_workqueue_38>`
                
                        * :ref:`Module macros <schedule_workqueue_39>`

                        * :ref:`Workqueue Handler Function <schedule_workqueue_40>`

                        * :ref:`Queue Start Function <schedule_workqueue_41>`

                        * :ref:`Queue Init Function <schedule_workqueue_42>`

                        * :ref:`Queue Stop Function <schedule_workqueue_43>`

                        * :ref:`Queue Exit Function <schedule_workqueue_44>`

                        * :ref:`Driver entry points <schedule_workqueue_45>`

                        * :ref:`See the full program below <schedule_workqueue_46>`

                        * :ref:`Makefile <schedule_workqueue_47>`

                        * :ref:`Compile and Load <schedule_workqueue_48>`
                
                * :ref:`Example 4 : Scheduling the workqueue <schedule_workqueue_49>`

                        * :ref:`List of headers <schedule_workqueue_50>`
                
                        * :ref:`Module macros <schedule_workqueue_51>`

                        * :ref:`Workqueue Handler Function <schedule_workqueue_52>`

                        * :ref:`Queue Start Function <schedule_workqueue_53>`

                        * :ref:`Queue Init Function <schedule_workqueue_54>`

                        * :ref:`Queue Stop Function <schedule_workqueue_55>`

                        * :ref:`Queue Exit Function <schedule_workqueue_56>`

                        * :ref:`Driver entry points <schedule_workqueue_57>`

                        * :ref:`See the full program below <schedule_workqueue_58>`

                        * :ref:`Makefile <schedule_workqueue_59>`

                        * :ref:`Compile and Load <schedule_workqueue_60>`

.. _schedule_workqueue_0:
 
.. tab-set::
 
    .. tab-item:: Version Info

        =============================== =======================================
        #                               Version
        =============================== =======================================
        Ubuntu                          Ubuntu 22.10
        Kernel                          6.8.0
        =============================== =======================================

.. _schedule_workqueue_1:

.. tab-set::

    .. tab-item:: Learnings in this section

        * In this program, you are going to learn

        .. panels::
                :container: container pb-4
                :column: col-lg-12 p-2
                :card: shadow

                * How to create workqueue ?

        .. panels::
                :container: container pb-4
                :column: col-lg-12 p-2
                :card: shadow

                * How to allocate the work to the queue ?

        .. panels::
                :container: container pb-4
                :column: col-lg-12 p-2
                :card: shadow

                * How to use Workqueue APIs ?

                        * `INIT_WORK <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L244>`_

                        * `schedule_work_on <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L543>`_

                        * `cancel_work_sync <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L457>`_

                        * `INIT_DELAYED_WORK <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L266>`_ 
                        
                        * `schedule_delayed_work_on <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L653>`_

                        * `cancel_delayed_work_sync <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L461>`_
                      
                        * `work_on_cpu <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L683>`_

                        * `work_on_cpu_safe <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L684>`_
 

        .. panels::
                :container: container pb-4
                :column: col-lg-12 p-2
                :card: shadow

                * How to use below APIs ?

                        * `MODULE_LICENSE <https://elixir.bootlin.com/linux/v6.7.9/source/include/linux/module.h#L230>`_

                        * `MODULE_DESCRIPTION <https://elixir.bootlin.com/linux/v6.7.9/source/include/linux/module.h#L239>`_

                        * `MODULE_AUTHOR <https://elixir.bootlin.com/linux/v6.7.9/source/include/linux/module.h#L236>`_

                        * `module_init <https://elixir.bootlin.com/linux/v6.7.9/source/include/linux/module.h#L88>`_

                        * `module_exit <https://elixir.bootlin.com/linux/v6.7.9/source/include/linux/module.h#L100>`_

.. _schedule_workqueue_2:

.. tab-set::

    .. tab-item:: Explanation of workqueue APIs

        .. _schedule_workqueue_3:

        .. tab-set::

            .. tab-item:: INIT_WORK

                * Here is the function prototype of the API: `INIT_WORK <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L244>`_

                .. code-block:: c

                        #include <linux/workqueue.h>
                        
                        #define INIT_WORK(_work, _func)

                * Here is an example of how to use the API,

                .. code-block:: c
        
                        INIT_WORK(&my_work_1,workqueue_func_1);     

        .. _schedule_workqueue_4:

        .. tab-set::

            .. tab-item:: schedule_work_on

                * Here is the function prototype of the API: `schedule_work_on <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L543>`_

                .. code-block:: c

                        #include <linux/workqueue.h>

                        static inline bool schedule_work_on(int cpu, struct work_struct *work);

                * Here is an example of how to use the API,
                       
                .. code-block:: c
                                
                        schedule_work_on(0,&my_work_1);

        .. _schedule_workqueue_5:

        .. tab-set::

            .. tab-item:: cancel_work_sync

                * Here is the function prototype of the API: `cancel_work_sync <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L457>`_

                .. code-block:: c

                        #include <linux/workqueue.h>
                        
                        extern bool cancel_work_sync(struct work_struct *work);

                * Here is an example of how to use the API,

                .. code-block:: c
        
                        cancel_work_sync(&my_work_1);

        .. _schedule_workqueue_6:

        .. tab-set::

            .. tab-item:: INIT_DELAYED_WORK

                * Here is the function prototype of the API: `INIT_DELAYED_WORK <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L266>`_

                .. code-block:: c

                        #include <linux/workqueue.h>
        
                        #define INIT_DELAYED_WORK(_work, _func)

                * Here is an example of how to use the API,

                .. code-block:: c

                        INIT_DELAYED_WORK(&my_work_1,workqueue_func_1);

        .. _schedule_workqueue_7:

        .. tab-set::

            .. tab-item:: schedule_delayed_work_on

                * Here is the function prototype of the API: `schedule_delayed_work_on <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L653>`_

                .. code-block:: c

                        #include <linux/workqueue.h>
        
                        static inline bool schedule_delayed_work_on(int cpu, struct delayed_work *dwork, unsigned long delay);

                * Here is an example of how to use the API,

                .. code-block:: c

                        schedule_delayed_work_on(0,&my_work_1,msecs_to_jiffies(100));                        

        .. _schedule_workqueue_8:

        .. tab-set::

            .. tab-item:: cancel_delayed_work_sync

                * Here is the function prototype of the API: `cancel_delayed_work_sync <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L461>`_

                .. code-block:: c

                        #include <linux/workqueue.h>

                        extern bool cancel_delayed_work_sync(struct delayed_work *dwork);

                * Here is an example of how to use the API,

                .. code-block:: c

                        cancel_delayed_work_sync(&my_work_1);
        
        .. _schedule_workqueue_9:

        .. tab-set::

            .. tab-item:: work_on_cpu

                * Here is the function prototype of the API: `work_on_cpu <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L683>`_

                .. code-block:: c

                        #include <linux/workqueue.h>

                        static inline long work_on_cpu(int cpu, long (*fn)(void *), void *arg);

                * Here is an example of how to use the API,

                .. code-block:: c
        
                        work_on_cpu(0,workqueue_func_1,NULL);
                        work_on_cpu(0,workqueue_func_2,NULL);
 
        .. _schedule_workqueue_10:

        .. tab-set::

            .. tab-item:: work_on_cpu_safe

                * Here is the function prototype of the API: `work_on_cpu_safe <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L684>`_

                .. code-block:: c

                        #include <linux/workqueue.h>

                        static inline long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg);

                * Here is an example of how to use the API,

                .. code-block:: c
        
                        work_on_cpu_safe(0,workqueue_func_1,NULL);
                        work_on_cpu_safe(0,workqueue_func_2,NULL);

.. _schedule_workqueue_11:

.. tab-set::

    .. tab-item:: Example 1 : Scheduling the workqueue

        * In this example let's see how to schedule workqueue and execute it.

        .. _schedule_workqueue_12:

        .. tab-set::

            .. tab-item:: List of headers

                * Include the follow header files(.h) to refer the API being used for the execution.

                .. code-block:: c

                        #include <linux/init.h>
                        #include <linux/kernel.h>
                        #include <linux/module.h>
                        #include <linux/workqueue.h>
                        #include <linux/delay.h>
                        #include <linux/jiffies.h>

        .. _schedule_workqueue_13:

        .. tab-set::

            .. tab-item:: Module macros

                * Add the following module macros to display information about the license, author and description about the module.

                .. code-block:: c

                        MODULE_LICENSE("GPL");
                        MODULE_AUTHOR("Linux_usr");
                        MODULE_DESCRIPTION("Example of schedule_work_on");

        .. _schedule_workqueue_14:

        .. tab-set::

            .. tab-item:: Initialize work

                * Initialize the work which we are going to use in this example

                .. code-block:: c

                        INIT_WORK(&my_work_1,workqueue_func_1);

        .. _schedule_workqueue_15:

        .. tab-set::

            .. tab-item:: Workqueue Handler Function

                * This function executes when work is queued to workqueue.

                .. code-block:: c

                        void workqueue_func_1(struct work_struct *work)
			{
			    int i = 0;
			    while (i < 10) {
				pr_info("Inside workqueue_func_1\n");
				i++;
				msleep(500);
			    }
			}

        .. _schedule_workqueue_16:

        .. tab-set::

            .. tab-item:: Queue Start Function

                * This function executes during execution of queue_start, creates workqueue, intiializes work and queues to the workqueue.

                .. code-block:: c

                        void queue_start(void)
                        {
                                INIT_WORK(&my_work_1,workqueue_func_1);
                                schedule_work_on(0,&my_work_1);
                        }
 
        .. _schedule_workqueue_17:

        .. tab-set::

            .. tab-item:: Queue Init Function

                * This function executes when module is loaded.

                .. code-block:: c

                        static int __init queue_init(void)
                        {
                                pr_info("Inside queue_init function\n");
                                queue_start();
                                return 0;
                        }

        .. _schedule_workqueue_18:

        .. tab-set::

            .. tab-item:: Queue Stop Function

                * This function executes during execution of queue_exit, waits until the completion and destroys workqueue.

                .. code-block:: c

                        void queue_stop(void)
                        {
                                pr_info("Destroying workqueue\n");
                                cancel_work_sync(&my_work_1);
                        }

        .. _schedule_workqueue_19:

        .. tab-set::

            .. tab-item:: Queue Exit Function

                * This function executes when module is unloaded.

                .. code-block:: c

                        static void __exit queue_exit(void)
                        {
                                pr_info("Inside queue_exit function\n");
                                queue_stop();
                                return;
                        }

        .. _schedule_workqueue_20:

        .. tab-set::

            .. tab-item:: Driver entry points

                * Add the driver entry points which will be executed once the module is inserted or removed from the kernel.

                .. code-block:: c

                        module_init(queue_init);
                        module_exit(queue_exit);

.. _schedule_workqueue_21:

.. tab-set::

    .. tab-item:: See the full program below

        .. tab-set::

            .. tab-item:: tc1.c
                
                .. literalinclude:: schedule_work/schedule_work_on/tc1.c
	            :language: c
        	    :linenos:

.. _schedule_workqueue_22:

.. tab-set::

    .. tab-item:: Makefile

	.. literalinclude:: schedule_work/schedule_work_on/Makefile
		:language: c
		:linenos:

.. _schedule_workqueue_23:

.. tab-set::

    .. tab-item:: Compile and Load
        
        * Run make to load the kernel module.

        .. code-block:: shell

                $ make

        * Check if work_queue.ko is generated or not using ls command.

        .. code-block:: shell

                $ ls -l
                total 376
		-rw-rw-r-- 1 test test    151 Aug  2 11:42 Makefile
		-rw-rw-r-- 1 test test     77 Aug  2 13:00 modules.order
		-rw-rw-r-- 1 test test      0 Aug  2 13:00 Module.symvers
		-rw-rw-r-- 1 test test   1604 Aug  2 11:42 tc1.c
		-rw-rw-r-- 1 test test 179336 Aug  2 13:00 tc1.ko
		-rw-rw-r-- 1 test test     77 Aug  2 13:00 tc1.mod
		-rw-rw-r-- 1 test test   1095 Aug  2 13:00 tc1.mod.c
		-rw-rw-r-- 1 test test 149280 Aug  2 13:00 tc1.mod.o
		-rw-rw-r-- 1 test test  31528 Aug  2 13:00 tc1.o

        * Load the module to kernel using insmod command.

        .. code-block:: shell

                $ sudo insmod ./tc1.ko
           
        * Check kernel messages to verify if the module is loaded or not.

        .. code-block:: shell
                
                $ dmesg
                [ 2501.281318] Inside queue_init function
		[ 2501.281378] Inside workqueue_func_1
		[ 2501.786594] Inside workqueue_func_1
		[ 2502.298749] Inside workqueue_func_1
		[ 2502.810724] Inside workqueue_func_1
		[ 2503.322661] Inside workqueue_func_1
		[ 2503.834783] Inside workqueue_func_1
		[ 2504.346752] Inside workqueue_func_1
		[ 2504.858631] Inside workqueue_func_1
		[ 2505.370734] Inside workqueue_func_1
		[ 2505.882749] Inside workqueue_func_1
         
        * Unload the module using rmmod command.

        .. code-block:: shell
                
                $ sudo rmmod tc1 

        * Check kernel messages to see if the module is unloaded or not.

        .. code-block:: shell

                $ dmesg
                [ 2531.335261] Inside queue_exit function
                [ 2531.335267] Destroying workqueue

.. _schedule_workqueue_24:

.. tab-set::

    .. tab-item:: Example 2 : Scheduling the workqueue

        * In this example let's see how to schedule workqueue and execute it.

        .. _schedule_workqueue_25:

        .. tab-set::

            .. tab-item:: List of headers

                * Include the follow header files(.h) to refer the API being used for the execution.

                .. code-block:: c

                        #include <linux/init.h>
                        #include <linux/kernel.h>
                        #include <linux/module.h>
                        #include <linux/workqueue.h>
                        #include <linux/delay.h>
                        #include <linux/jiffies.h>

        .. _schedule_workqueue_26:

        .. tab-set::

            .. tab-item:: Module macros

                * Add the following module macros to display information about the license, author and description about the module.

                .. code-block:: c

                        MODULE_LICENSE("GPL");
                        MODULE_AUTHOR("Linux_usr");
                        MODULE_DESCRIPTION("Example of schedule_delayed_work_on");

        .. _schedule_workqueue_27:

        .. tab-set::

            .. tab-item:: Initialize work

                * Initialize the work which we are going to use in this example

                .. code-block:: c

                        INIT_WORK(&my_work_1,workqueue_func_1);

        .. _schedule_workqueue_28:

        .. tab-set::

            .. tab-item:: Workqueue Handler Function

                * This function executes when work is queued to workqueue.

                .. code-block:: c

                        void workqueue_func_1(struct work_struct *work)
			{
			    int i = 0;
			    while (i < 10) {
				pr_info("Inside workqueue_func_1\n");
				i++;
				msleep(500);
			    }
			}

        .. _schedule_workqueue_29:

        .. tab-set::

            .. tab-item:: Queue Start Function

                * This function executes during execution of queue_start, creates workqueue, intiializes work and queues to the workqueue.

                .. code-block:: c

                        void queue_start(void)
                        {
                                INIT_WORK(&my_work_1,workqueue_func_1);
                                schedule_delayed_work_on(0,&my_work_1,msecs_to_jiffies(100));
                        }
 
        .. _schedule_workqueue_30:

        .. tab-set::

            .. tab-item:: Queue Init Function

                * This function executes when module is loaded.

                .. code-block:: c

                        static int __init queue_init(void)
                        {
                                pr_info("Inside queue_init function\n");
                                queue_start();
                                return 0;
                        }

        .. _schedule_workqueue_31:

        .. tab-set::

            .. tab-item:: Queue Stop Function

                * This function executes during execution of queue_exit, waits until the completion and destroys workqueue.

                .. code-block:: c

                        void queue_stop(void)
                        {
                                pr_info("Destroying workqueue\n");
                                cancel_delayed_work_sync(&my_work_1);
                        }

        .. _schedule_workqueue_32:

        .. tab-set::

            .. tab-item:: Queue Exit Function

                * This function executes when module is unloaded.

                .. code-block:: c

                        static void __exit queue_exit(void)
                        {
                                pr_info("Inside queue_exit function\n");
                                queue_stop();
                                return;
                        }

        .. _schedule_workqueue_33:

        .. tab-set::

            .. tab-item:: Driver entry points

                * Add the driver entry points which will be executed once the module is inserted or removed from the kernel.

                .. code-block:: c

                        module_init(queue_init);
                        module_exit(queue_exit);

.. _schedule_workqueue_34:

.. tab-set::

    .. tab-item:: See the full program below

        .. tab-set::

            .. tab-item:: tc2.c
                
                .. literalinclude:: schedule_work/schedule_delayed_work_on/tc2.c
	            :language: c
        	    :linenos:

.. _schedule_workqueue_35:

.. tab-set::

    .. tab-item:: Makefile

	.. literalinclude:: schedule_work/schedule_delayed_work_on/Makefile
		:language: c
		:linenos:

.. _schedule_workqueue_36:

.. tab-set::

    .. tab-item:: Compile and Load
        
        * Run make to load the kernel module.

        .. code-block:: shell

                $ make

        * Check if work_queue.ko is generated or not using ls command.

        .. code-block:: shell

                $ ls -l
                total 376
		-rw-rw-r-- 1 test test    151 Aug  2 12:58 Makefile
		-rw-rw-r-- 1 test test     85 Aug  2 12:58 modules.order
		-rw-rw-r-- 1 test test      0 Aug  2 12:58 Module.symvers
		-rw-rw-r-- 1 test test   1659 Aug  2 11:42 tc2.c
		-rw-rw-r-- 1 test test 179712 Aug  2 12:58 tc2.ko
		-rw-rw-r-- 1 test test     85 Aug  2 12:58 tc2.mod
		-rw-rw-r-- 1 test test   1189 Aug  2 12:58 tc2.mod.c
		-rw-rw-r-- 1 test test 149424 Aug  2 12:58 tc2.mod.o
		-rw-rw-r-- 1 test test  31728 Aug  2 12:58 tc2.o

        * Load the module to kernel using insmod command.

        .. code-block:: shell

                $ sudo insmod ./tc2.ko
           
        * Check kernel messages to verify if the module is loaded or not.

        .. code-block:: shell
                
                $ dmesg
                [ 2358.328633] Inside queue_init function
		[ 2358.430764] Inside workqueue_func_1
		[ 2358.938739] Inside workqueue_func_1
		[ 2359.450680] Inside workqueue_func_1
		[ 2359.962748] Inside workqueue_func_1
		[ 2360.474731] Inside workqueue_func_1
		[ 2360.986714] Inside workqueue_func_1
		[ 2361.498682] Inside workqueue_func_1
		[ 2362.010688] Inside workqueue_func_1
		[ 2362.522739] Inside workqueue_func_1
		[ 2363.034725] Inside workqueue_func_1
           
        * Unload the module using rmmod command.

        .. code-block:: shell
                
                $ sudo rmmod tc2

        * Check kernel messages to see if the module is unloaded or not.

        .. code-block:: shell

                $ dmesg
                [ 2391.552930] Inside queue_exit function
                [ 2391.552940] Destroying workqueue

.. _schedule_workqueue_37:

.. tab-set::

    .. tab-item:: Example 3 : Scheduling the workqueue

        * In this example let's see how to schedule workqueue and execute it.

        .. _schedule_workqueue_38:

        .. tab-set::

            .. tab-item:: List of headers

                * Include the follow header files(.h) to refer the API being used for the execution.

                .. code-block:: c

                        #include <linux/init.h>
                        #include <linux/kernel.h>
                        #include <linux/module.h>
                        #include <linux/workqueue.h>
                        #include <linux/delay.h>
                        #include <linux/jiffies.h>

        .. _schedule_workqueue_39:

        .. tab-set::

            .. tab-item:: Module macros

                * Add the following module macros to display information about the license, author and description about the module.

                .. code-block:: c

                        MODULE_LICENSE("GPL");
                        MODULE_AUTHOR("Linux_usr");
                        MODULE_DESCRIPTION("Example of work_on_cpu");

        .. _schedule_workqueue_40:

        .. tab-set::

            .. tab-item:: Workqueue Handler Function

                * This workqueue_func_1 function executes when work is queued to workqueue.

                .. code-block:: c

                        long int workqueue_func_1(struct work_struct *work)
			{
			    int i = 0;
			    while (i < 10) {
				pr_info("Inside workqueue_func_1\n");
				i++;
				msleep(500);
			    }
			}

                * This workqueue_func_2 function executes when work is queued to workqueue.

                .. code-block:: c

                        long int workqueue_func_2(struct work_struct *work)
			{
			    int i = 0;
			    while (i < 10) {
				pr_info("Inside workqueue_func_2\n");
				i++;
				msleep(500);
			    }
			}


        .. _schedule_workqueue_41:

        .. tab-set::

            .. tab-item:: Queue Start Function

                * This function executes during execution of queue_start, creates workqueue, intiializes work and queues to the workqueue.

                .. code-block:: c

                        void queue_start(void)
                        {
                                work_on_cpu(0,workqueue_func_1,NULL);
                                work_on_cpu(0,workqueue_func_2,NULL);
                        }
 
        .. _schedule_workqueue_42:

        .. tab-set::

            .. tab-item:: Queue Init Function

                * This function executes when module is loaded.

                .. code-block:: c

                        static int __init queue_init(void)
                        {
                                pr_info("Inside queue_init function\n");
                                queue_start();
                                return 0;
                        }

        .. _schedule_workqueue_43:

        .. tab-set::

            .. tab-item:: Queue Stop Function

                * This function executes during execution of queue_exit, waits until the completion and destroys workqueue.

                .. code-block:: c

                        void queue_stop(void)
                        {
                                pr_info("Destroying workqueue\n");
                        }

        .. _schedule_workqueue_44:

        .. tab-set::

            .. tab-item:: Queue Exit Function

                * This function executes when module is unloaded.

                .. code-block:: c

                        static void __exit queue_exit(void)
                        {
                                pr_info("Inside queue_exit function\n");
                                queue_stop();
                                return;
                        }

        .. _schedule_workqueue_45:

        .. tab-set::

            .. tab-item:: Driver entry points

                * Add the driver entry points which will be executed once the module is inserted or removed from the kernel.

                .. code-block:: c

                        module_init(queue_init);
                        module_exit(queue_exit);

.. _schedule_workqueue_46:

.. tab-set::

    .. tab-item:: See the full program below

        .. tab-set::

            .. tab-item:: tc3.c
                
                .. literalinclude:: schedule_work/work_on_cpu/tc3.c
	            :language: c
        	    :linenos:

.. _schedule_workqueue_47:

.. tab-set::

    .. tab-item:: Makefile

	.. literalinclude:: schedule_work/work_on_cpu/Makefile
		:language: c
		:linenos:

.. _schedule_workqueue_48:

.. tab-set::

    .. tab-item:: Compile and Load
        
        * Run make to load the kernel module.

        .. code-block:: shell

                $ make

        * Check if work_queue.ko is generated or not using ls command.

        .. code-block:: shell

                $ ls -l
                total 368
		-rw-rw-r-- 1 test test    151 Aug  2 11:42 Makefile
		-rw-rw-r-- 1 test test     72 Aug  2 13:02 modules.order
		-rw-rw-r-- 1 test test      0 Aug  2 13:02 Module.symvers
		-rw-rw-r-- 1 test test   1826 Aug  2 11:42 tc3.c
		-rw-rw-r-- 1 test test 175808 Aug  2 13:02 tc3.ko
		-rw-rw-r-- 1 test test     72 Aug  2 13:02 tc3.mod
		-rw-rw-r-- 1 test test   1031 Aug  2 13:02 tc3.mod.c
		-rw-rw-r-- 1 test test 149144 Aug  2 13:02 tc3.mod.o
		-rw-rw-r-- 1 test test  28160 Aug  2 13:02 tc3.o

        * Load the module to kernel using insmod command.

        .. code-block:: shell

                $ sudo insmod ./tc3.ko
           
        * Check kernel messages to verify if the module is loaded or not.

        .. code-block:: shell
                
                $ dmesg
                [ 2586.720879] Inside queue_init function
		[ 2586.720925] Inside workqueue_func_1
		[ 2587.226675] Inside workqueue_func_1
		[ 2587.738795] Inside workqueue_func_1
		[ 2588.250747] Inside workqueue_func_1
		[ 2588.762771] Inside workqueue_func_1
		[ 2589.274774] Inside workqueue_func_1
		[ 2589.786797] Inside workqueue_func_1
		[ 2590.298791] Inside workqueue_func_1
		[ 2590.810741] Inside workqueue_func_1
		[ 2591.322597] Inside workqueue_func_1
		[ 2591.834882] Inside workqueue_func_2
		[ 2592.346790] Inside workqueue_func_2
		[ 2592.858774] Inside workqueue_func_2
		[ 2593.370736] Inside workqueue_func_2
		[ 2593.882757] Inside workqueue_func_2
		[ 2594.394540] Inside workqueue_func_2
		[ 2594.906671] Inside workqueue_func_2
		[ 2595.418783] Inside workqueue_func_2
		[ 2595.930782] Inside workqueue_func_2
		[ 2596.442785] Inside workqueue_func_2
         
        * Unload the module using rmmod command.

        .. code-block:: shell
                
                $ sudo rmmod tc3

        * Check kernel messages to see if the module is unloaded or not.

        .. code-block:: shell

                $ dmesg
                [ 2614.919189] Inside queue_exit function
                [ 2614.919199] Destroying workqueue

.. _schedule_workqueue_49:

.. tab-set::

    .. tab-item:: Example 4 : Scheduling the workqueue

        * In this example let's see how to schedule workqueue and execute it.

        .. _schedule_workqueue_50:

        .. tab-set::

            .. tab-item:: List of headers

                * Include the follow header files(.h) to refer the API being used for the execution.

                .. code-block:: c

                        #include <linux/init.h>
                        #include <linux/kernel.h>
                        #include <linux/module.h>
                        #include <linux/workqueue.h>
                        #include <linux/delay.h>
                        #include <linux/jiffies.h>

        .. _schedule_workqueue_51:

        .. tab-set::

            .. tab-item:: Module macros

                * Add the following module macros to display information about the license, author and description about the module.

                .. code-block:: c

                        MODULE_LICENSE("GPL");
                        MODULE_AUTHOR("Linux_usr");
                        MODULE_DESCRIPTION("Example of work_on_cpu_safe");

        .. _schedule_workqueue_52:

        .. tab-set::

            .. tab-item:: Workqueue Handler Function

                * This workqueue_func_1 function executes when work is queued to workqueue.

                .. code-block:: c

                        long int workqueue_func_1(struct work_struct *work)
			{
			    int i = 0;
			    while (i < 10) {
				pr_info("Inside workqueue_func_1\n");
				i++;
				msleep(500);
			    }
			}

                * This workqueue_func_2 function executes when work is queued to workqueue.

                .. code-block:: c

                        long int workqueue_func_2(struct work_struct *work)
			{
			    int i = 0;
			    while (i < 10) {
				pr_info("Inside workqueue_func_2\n");
				i++;
				msleep(500);
			    }
			}


        .. _schedule_workqueue_53:

        .. tab-set::

            .. tab-item:: Queue Start Function

                * This function executes during execution of queue_start, creates workqueue, intiializes work and queues to the workqueue.

                .. code-block:: c

                        void queue_start(void)
                        {
                                work_on_cpu_safe(0,workqueue_func_1,NULL);
                                work_on_cpu_safe(0,workqueue_func_2,NULL);
                        }
 
        .. _schedule_workqueue_54:

        .. tab-set::

            .. tab-item:: Queue Init Function

                * This function executes when module is loaded.

                .. code-block:: c

                        static int __init queue_init(void)
                        {
                                pr_info("Inside queue_init function\n");
                                queue_start();
                                return 0;
                        }

        .. _schedule_workqueue_55:

        .. tab-set::

            .. tab-item:: Queue Stop Function

                * This function executes during execution of queue_exit, waits until the completion and destroys workqueue.

                .. code-block:: c

                        void queue_stop(void)
                        {
                                pr_info("Destroying workqueue\n");
                        }

        .. _schedule_workqueue_56:

        .. tab-set::

            .. tab-item:: Queue Exit Function

                * This function executes when module is unloaded.

                .. code-block:: c

                        static void __exit queue_exit(void)
                        {
                                pr_info("Inside queue_exit function\n");
                                queue_stop();
                                return;
                        }

        .. _schedule_workqueue_57:

        .. tab-set::

            .. tab-item:: Driver entry points

                * Add the driver entry points which will be executed once the module is inserted or removed from the kernel.

                .. code-block:: c

                        module_init(queue_init);
                        module_exit(queue_exit);

.. _schedule_workqueue_58:

.. tab-set::

    .. tab-item:: See the full program below

        .. tab-set::

            .. tab-item:: tc4.c
                
                .. literalinclude:: schedule_work/work_on_cpu_safe/tc4.c
	            :language: c
        	    :linenos:

.. _schedule_workqueue_59:

.. tab-set::

    .. tab-item:: Makefile

	.. literalinclude:: schedule_work/work_on_cpu_safe/Makefile
		:language: c
		:linenos:

.. _schedule_workqueue_60:

.. tab-set::

    .. tab-item:: Compile and Load
        
        * Run make to load the kernel module.

        .. code-block:: shell

                $ make

        * Check if work_queue.ko is generated or not using ls command.

        .. code-block:: shell

                $ ls -l
                total 368
		-rw-rw-r-- 1 test test    151 Aug  2 11:42 Makefile
		-rw-rw-r-- 1 test test     77 Aug  2 13:06 modules.order
		-rw-rw-r-- 1 test test      0 Aug  2 13:06 Module.symvers
		-rw-rw-r-- 1 test test   1836 Aug  2 11:42 tc4.c
		-rw-rw-r-- 1 test test 175832 Aug  2 13:06 tc4.ko
		-rw-rw-r-- 1 test test     77 Aug  2 13:06 tc4.mod
		-rw-rw-r-- 1 test test   1036 Aug  2 13:06 tc4.mod.c
		-rw-rw-r-- 1 test test 149152 Aug  2 13:06 tc4.mod.o
		-rw-rw-r-- 1 test test  28184 Aug  2 13:06 tc4.o

        * Load the module to kernel using insmod command.

        .. code-block:: shell

                $ sudo insmod ./tc4.ko
           
        * Check kernel messages to verify if the module is loaded or not.

        .. code-block:: shell
                
                $ dmesg
                [ 2840.301249] Inside queue_init function
		[ 2840.301327] Inside workqueue_func_1
		[ 2840.826763] Inside workqueue_func_1
		[ 2841.338795] Inside workqueue_func_1
		[ 2841.850758] Inside workqueue_func_1
		[ 2842.362763] Inside workqueue_func_1
		[ 2842.874753] Inside workqueue_func_1
		[ 2843.386787] Inside workqueue_func_1
		[ 2843.898748] Inside workqueue_func_1
		[ 2844.410762] Inside workqueue_func_1
		[ 2844.922632] Inside workqueue_func_1
		[ 2845.434911] Inside workqueue_func_2
		[ 2845.946770] Inside workqueue_func_2
		[ 2846.458715] Inside workqueue_func_2
		[ 2846.970762] Inside workqueue_func_2
		[ 2847.482759] Inside workqueue_func_2
		[ 2847.994557] Inside workqueue_func_2
		[ 2848.506718] Inside workqueue_func_2
		[ 2849.018758] Inside workqueue_func_2
		[ 2849.530761] Inside workqueue_func_2
		[ 2850.042761] Inside workqueue_func_2

        * Unload the module using rmmod command.

        .. code-block:: shell
                
                $ sudo rmmod tc4

        * Check kernel messages to see if the module is unloaded or not.

        .. code-block:: shell

                $ dmesg
                [ 2866.416509] Inside queue_exit function
                [ 2866.416516] Destroying workqueue