Destroy Work
============

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

        Topics in this section,

                * :ref:`Version Info <destroy_work_0>`

                * :ref:`Learnings in this program <destroy_work_1>`
                
                * :ref:`Explanation of Workqueue APIs <destroy_work_2>`

                        * :ref:`create_workqueue <destroy_work_3>`

                        * :ref:`INIT_WORK <destroy_work_4>`

                        * :ref:`queue_work <destroy_work_5>`
                        
                        * :ref:`destroy_workqueue <destroy_work_6>`       

                * :ref:`Example 1 : Destroying the workqueue <destroy_work_18>`

                        * :ref:`List of headers <destroy_work_19>`
                
                        * :ref:`Module macros <destroy_work_20>`

                        * :ref:`Initializing work <destroy_work_21>`

                        * :ref:`Workqueue Handler Function <destroy_work_22>`

                        * :ref:`Queue Start Function <destroy_work_23>`

                        * :ref:`Queue Init Function <destroy_work_24>`

                        * :ref:`Queue Stop Function <destroy_work_25>`

                        * :ref:`Queue Exit Function <destroy_work_26>`

                        * :ref:`Driver entry points <destroy_work_27>`

                        * :ref:`See the full program below <destroy_work_28>`

                        * :ref:`Makefile <destroy_work_29>`

                        * :ref:`Compile and Load <destroy_work_30>`

                * :ref:`Example 2 : Destroying the workqueue <destroy_work_31>`

                        * :ref:`List of headers <destroy_work_32>`
                
                        * :ref:`Module macros <destroy_work_33>`

                        * :ref:`Initializing work <destroy_work_34>`

                        * :ref:`Workqueue Handler Function <destroy_work_35>`

                        * :ref:`Queue Start Function <destroy_work_36>`

                        * :ref:`Queue Init Function <destroy_work_37>`

                        * :ref:`Queue Stop Function <destroy_work_38>`

                        * :ref:`Queue Exit Function <destroy_work_39>`

                        * :ref:`Driver entry points <destroy_work_40>`

                        * :ref:`See the full program below <destroy_work_41>`

                        * :ref:`Makefile <destroy_work_42>`

                        * :ref:`Compile and Load <destroy_work_43>`

                * :ref:`Example 3 : Destroying the workqueue <destroy_work_44>`

                        * :ref:`List of headers <destroy_work_45>`
                
                        * :ref:`Module macros <destroy_work_46>`

                        * :ref:`Initializing work <destroy_work_47>`

                        * :ref:`Workqueue Handler Function <destroy_work_48>`

                        * :ref:`Queue Start Function <destroy_work_49>`

                        * :ref:`Queue Init Function <destroy_work_50>`

                        * :ref:`Queue Stop Function <destroy_work_51>`

                        * :ref:`Queue Exit Function <destroy_work_52>`

                        * :ref:`Driver entry points <destroy_work_53>`

                        * :ref:`See the full program below <destroy_work_54>`

                        * :ref:`Makefile <destroy_work_55>`

                        * :ref:`Compile and Load <destroy_work_56>`

                * :ref:`Example 2 : Destroying the workqueue <destroy_work_57>`

                        * :ref:`List of headers <destroy_work_58>`
                
                        * :ref:`Module macros <destroy_work_59>`

                        * :ref:`Initializing work <destroy_work_60>`

                        * :ref:`Workqueue Handler Function <destroy_work_61>`

                        * :ref:`Queue Start Function <destroy_work_62>`

                        * :ref:`Queue Init Function <destroy_work_63>`

                        * :ref:`Queue Stop Function <destroy_work_64>`

                        * :ref:`Queue Exit Function <destroy_work_65>`

                        * :ref:`Driver entry points <destroy_work_66>`

                        * :ref:`See the full program below <destroy_work_67>`

                        * :ref:`Makefile <destroy_work_68>`

                        * :ref:`Compile and Load <destroy_work_69>`




.. _destroy_work_0:
 
.. tab-set::
 
    .. tab-item:: Version Info

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

.. _destroy_work_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 ?

                        * `create_workqueue <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L422>`_

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

                        * `queue_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L500>`_

                        * `destroy_workqueue <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L430>`_

                        * `INIT_DELAYED_WORK <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L266>`_ 
                       
                        * `delayed_work_pending <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L296>`_

                        * `schedule_delayed_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L667>`_
                        
                        * `cancel_delayed_work_sync <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L461>`_
                        
                        * `cancel_delayed_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L460>`_
                          
                        * `work_pending <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L288>`_
                        
                        * `schedule_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L562>`_

                        * `cancel_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L456>`_

                        

        .. 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>`_

.. _destroy_work_2:

.. tab-set::

    .. tab-item:: Explanation of workqueue APIs

        .. _destroy_work_3:

        .. tab-set::

            .. tab-item:: create_workqueue

                * Here is the function prototype of the API: `create_workqueue <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L422>`_

                .. code-block:: c

                        #include <linux/workqueue.h>
                        
                        #define create_workqueue(name)

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

                .. code-block:: c

                        my_workqueue = create_workqueue(WQ_NAME);

        .. _destroy_work_4:

        .. 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);     

        .. _destroy_work_5:

        .. tab-set::

            .. tab-item:: queue_work

                * Here is the function prototype of the API: `queue_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L500>`_ 

                .. code-block:: c

                        #include <linux/workqueue.h>
                        
                        static inline bool queue_work(struct workqueue_struct *wq, struct work_struct *work);

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

                .. code-block:: c

                        queue_work(my_workqueue,&my_work_1);

        .. _destroy_work_6:

        .. tab-set::

            .. tab-item:: destroy_workqueue

                * Here is the function prototype of the API: `queue_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L500>`_ 

                .. code-block:: c

                        #include <linux/workqueue.h>
                        
                        extern void destroy_workqueue(struct workqueue_struct *wq);

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

                .. code-block:: c
        
                        destroy_workqueue(my_workqueue);

        .. _destroy_work_7:

        .. tab-set::

            .. tab-item:: work_pending

                * Here is the function prototype of the API: `work_pending <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L288>`_

                .. code-block:: c

                        #include <linux/workqueue.h>

                        #define work_pending(work)

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

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

        .. _destroy_work_8:

        .. 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);
                        INIT_DELAYED_WORK(&my_work_2,workqueue_func_2);
        
        .. _destroy_work_9:

        .. tab-set::

            .. tab-item:: delayed_work_pending

                * Here is the function prototype of the API: `delayed_work_pending <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L296>`_ 

                .. code-block:: c

                        #include <linux/workqueue.h>

                        #define delayed_work_pending(w)

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

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

        .. _destroy_work_10:

        .. 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);
                        cancel_delayed_work_sync(&my_work_2);
        
        .. _destroy_work_11:

        .. tab-set::

            .. tab-item:: schedule_work

                * Here is the function prototype of the API: `schedule_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L562>`_

                .. code-block:: c

                        #include <linux/workqueue.h>
                        
                        static inline bool schedule_work(struct work_struct *work);

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

                .. code-block:: c
        
                        schedule_work(&my_work_1);
                        schedule_work(&my_work_2);

        .. _destroy_work_12:

        .. tab-set::

            .. tab-item:: cancel_work 

                * Here is the function prototype of the API: `cancel_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L456>`_                
                
                .. code-block:: c

                        #include <linux/workqueue.h>

                        extern bool cancel_work(struct work_struct *work);

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

                .. code-block:: c

                        cancel_work(&my_work_1);
                        cancel_work(&my_work_2); 

        .. _destroy_work_13:

        .. tab-set::

            .. tab-item:: schedule_delayed_work

                * Here is the function prototype of the API: `schedule_delayed_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L667>`_

                .. code-block:: c

                        #include <linux/workqueue.h>

                        static inline bool schedule_delayed_work(struct delayed_work *dwork, unsigned long delay);

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

                .. code-block:: c
                        
                        schedule_delayed_work(&my_work,msecs_to_jiffies(100));

        .. _destroy_work_14:

        .. tab-set::

            .. tab-item:: cancel_delayed_work

                * Here is the function prototype of the API: `cancel_delayed_work <https://elixir.bootlin.com/linux/v6.2/source/include/linux/workqueue.h#L460>`_

                .. code-block:: c

                        #include <linux/workqueue.h>

                        extern bool cancel_delayed_work(struct delayed_work *dwork);

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

                .. code-block:: c
                        
                        cancel_delayed_work(&my_work);

.. _destroy_work_18:

.. tab-set::

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

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

        .. _destroy_work_19:

        .. 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>

        .. _destroy_work_20:

        .. 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 cancel_workqueue");

        .. _destroy_work_21:

        .. tab-set::

            .. tab-item:: Initializing work

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

                .. code-block:: c

                        INIT_WORK(&my_work_1,workqueue_func_1);
                        INIT_WORK(&my_work_2,workqueue_func_2);

        .. _destroy_work_22:

        .. tab-set::

            .. tab-item:: Workqueue Handler Function

                * This workqueue_func_1 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(1000);
                                }
                        }

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

                .. code-block:: c

                        void workqueue_func_2(struct work_struct *work)
                        {
                                int i = 0;
                                while (i < 10) {
                                        pr_info("Inside workqueue_func_1\n");
                                        i++;
                                        msleep(1000);
                                }
                        }


        .. _destroy_work_23:

        .. tab-set::

            .. tab-item:: Queue Start Function

                * This function creates workqueue, intiializes work and queues to the workqueue.

                .. code-block:: c

                        void queue_start(void)
			{
			    my_workqueue = create_workqueue(WQ_NAME);
			    INIT_WORK(&my_work_1,workqueue_func_1);
			    INIT_WORK(&my_work_2,workqueue_func_2);
			    if (!work_pending(&my_work_1)) {
				queue_work(my_workqueue,&my_work_1);
			    }
			    if (!work_pending(&my_work_2)) {
				queue_work(my_workqueue,&my_work_2);
			    }
			}

        .. _destroy_work_24:

        .. 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;
                        }

        .. _destroy_work_25:

        .. 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(&my_work_1);
                                cancel_work(&my_work_2);
                                destroy_workqueue(my_workqueue);
                        }

        .. _destroy_work_26:

        .. 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;
                        }

        .. _destroy_work_27:

        .. 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);

.. _destroy_work_28:

.. tab-set::

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

        .. tab-set::

            .. tab-item:: tc1.c
                
                .. literalinclude:: destroy_work/cancel_work/tc1.c
	            :language: c
        	    :linenos:

.. _destroy_work_29:

.. tab-set::

    .. tab-item:: Makefile

	.. literalinclude:: destroy_work/cancel_work/Makefile
		:language: c
		:linenos:

.. _destroy_work_30:

.. 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 384
		-rw-rw-r-- 1 test test    151 Aug  2 11:47 Makefile
		-rw-rw-r-- 1 test test     76 Aug  2 12:48 modules.order
		-rw-rw-r-- 1 test test      0 Aug  2 12:48 Module.symvers
		-rw-rw-r-- 1 test test   2040 Aug  2 11:47 tc1.c
		-rw-rw-r-- 1 test test 180944 Aug  2 12:48 tc1.ko
		-rw-rw-r-- 1 test test     76 Aug  2 12:48 tc1.mod
		-rw-rw-r-- 1 test test   1103 Aug  2 12:48 tc1.mod.c
		-rw-rw-r-- 1 test test 149280 Aug  2 12:48 tc1.mod.o
		-rw-rw-r-- 1 test test  33112 Aug  2 12:48 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
                [ 1812.726131] Inside queue_init function
                [ 1812.726612] Inside workqueue_func_2
                [ 1812.726979] Inside workqueue_func_1
                [ 1813.754717] Inside workqueue_func_1
                [ 1814.778711] Inside workqueue_func_1
                [ 1815.802723] Inside workqueue_func_1
                [ 1816.826704] Inside workqueue_func_1
                [ 1817.850705] Inside workqueue_func_1
                [ 1818.874707] Inside workqueue_func_1
                [ 1819.898722] Inside workqueue_func_1
                [ 1820.922729] Inside workqueue_func_1
                [ 1821.946714] 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
                [ 1835.094347] Inside queue_exit function


.. _destroy_work_31:

.. tab-set::

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

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

        .. _destroy_work_32:

        .. 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>

        .. _destroy_work_33:

        .. 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 flush_work");

        .. _destroy_work_34:

        .. tab-set::

            .. tab-item:: Initializing work

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

                .. code-block:: c

                        INIT_WORK(&my_work_1,workqueue_func_1);
                        INIT_WORK(&my_work_2,workqueue_func_2);

        .. _destroy_work_35:

        .. tab-set::

            .. tab-item:: Workqueue Handler Function

                * This workqueue_func_1 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(1000);
                                }
                        }

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

                .. code-block:: c

                        void workqueue_func_2(struct work_struct *work)
                        {
                                int i = 0;
                                while (i < 10) {
                                        pr_info("Inside workqueue_func_1\n");
                                        i++;
                                        msleep(1000);
                                }
                        }


        .. _destroy_work_36:

        .. tab-set::

            .. tab-item:: Queue Start Function

                * This function creates workqueue, intiializes work and queues to the workqueue.

                .. code-block:: c

                        void queue_start(void)
			{
			    my_workqueue = create_workqueue(WQ_NAME);
			    INIT_WORK(&my_work_1,workqueue_func_1);
			    INIT_WORK(&my_work_2,workqueue_func_2);
			    if (!work_pending(&my_work_1)) {
				queue_work(my_workqueue,&my_work_1);
			    }
			    if (!work_pending(&my_work_2)) {
				queue_work(my_workqueue,&my_work_2);
			    }
			}

        .. _destroy_work_37:

        .. 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;
                        }

        .. _destroy_work_38:

        .. 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");
                                flush_work(&my_work_1);
                                flush_work(&my_work_2);
                                destroy_workqueue(my_workqueue);
                        }

        .. _destroy_work_39:

        .. 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;
                        }

        .. _destroy_work_40:

        .. 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);

.. _destroy_work_41:

.. tab-set::

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

        .. tab-set::

            .. tab-item:: tc2.c
                
                .. literalinclude:: destroy_work/flush_work/tc2.c
	            :language: c
        	    :linenos:

.. _destroy_work_42:

.. tab-set::

    .. tab-item:: Makefile

	.. literalinclude:: destroy_work/flush_work/Makefile
		:language: c
		:linenos:

.. _destroy_work_43:

.. 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 384
		-rw-rw-r-- 1 test test    151 Aug  2 11:47 Makefile
		-rw-rw-r-- 1 test test     76 Aug  2 12:48 modules.order
		-rw-rw-r-- 1 test test      0 Aug  2 12:48 Module.symvers
		-rw-rw-r-- 1 test test   2040 Aug  2 11:47 tc2.c
		-rw-rw-r-- 1 test test 180944 Aug  2 12:48 tc2.ko
		-rw-rw-r-- 1 test test     76 Aug  2 12:48 tc2.mod
		-rw-rw-r-- 1 test test   1103 Aug  2 12:48 tc2.mod.c
		-rw-rw-r-- 1 test test 149280 Aug  2 12:48 tc2.mod.o
		-rw-rw-r-- 1 test test  33112 Aug  2 12:48 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
                [ 1812.726131] Inside queue_init function
                [ 1812.726612] Inside workqueue_func_2
                [ 1812.726979] Inside workqueue_func_1
                [ 1813.754717] Inside workqueue_func_1
                [ 1814.778711] Inside workqueue_func_1
                [ 1815.802723] Inside workqueue_func_1
                [ 1816.826704] Inside workqueue_func_1
                [ 1817.850705] Inside workqueue_func_1
                [ 1818.874707] Inside workqueue_func_1
                [ 1819.898722] Inside workqueue_func_1
                [ 1820.922729] Inside workqueue_func_1
                [ 1821.946714] 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
                [ 1835.094347] Inside queue_exit function

.. _destroy_work_44:

.. tab-set::

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

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

        .. _destroy_work_45:

        .. 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>

        .. _destroy_work_46:

        .. 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 flush_delayed_work");

        .. _destroy_work_47:

        .. tab-set::

            .. tab-item:: Initializing work

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

                .. code-block:: c

                        INIT_DELAYED_WORK(&my_work_1,workqueue_func_1);
                        INIT_DELAYED_WORK(&my_work_2,workqueue_func_2);

        .. _destroy_work_48:

        .. tab-set::

            .. tab-item:: Workqueue Handler Function

                * This workqueue_func_1 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(1000);
                                }
                        }

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

                .. code-block:: c

                        void workqueue_func_2(struct work_struct *work)
                        {
                                int i = 0;
                                while (i < 10) {
                                        pr_info("Inside workqueue_func_2\n");
                                        i++;
                                        msleep(1000);
                                }           
                        }

        .. _destroy_work_49:

        .. tab-set::

            .. tab-item:: Queue Start Function

                * This function creates workqueue, intiializes work and queues to the workqueue.

                .. code-block:: c

                        void queue_start(void)
                        {
                                my_workqueue = create_workqueue(WQ_NAME);
                                INIT_DELAYED_WORK(&my_work_1,workqueue_func_1);
                                INIT_DELAYED_WORK(&my_work_2,workqueue_func_2);
                                queue_delayed_work(my_workqueue,&my_work_1,msecs_to_jiffies(100));
                                queue_delayed_work(my_workqueue,&my_work_2,msecs_to_jiffies(300));
                        }
 
        .. _destroy_work_50:

        .. 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;
                        }

        .. _destroy_work_51:

        .. 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)
                        {
                                flush_delayed_work_sync(&my_work_1);
                                flush_delayed_work_sync(&my_work_2);
                                pr_info("Destroying workqueue\n");
                                destroy_workqueue(my_workqueue);
                        }

        .. _destroy_work_52:

        .. 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;
                        }

        .. _destroy_work_53:

        .. 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);

.. _destroy_work_54:

.. tab-set::

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

        .. tab-set::

            .. tab-item:: tc3.c
                
                .. literalinclude:: destroy_work/flush_delayed_work/tc3.c
	            :language: c
        	    :linenos:

.. _destroy_work_55:

.. tab-set::

    .. tab-item:: Makefile

	.. literalinclude:: destroy_work/flush_delayed_work/Makefile
		:language: c
		:linenos:

.. _destroy_work_56:

.. 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 388
		-rw-rw-r-- 1 test test    151 Aug  2 11:47 Makefile
		-rw-rw-r-- 1 test test     84 Aug  2 12:42 modules.order
		-rw-rw-r-- 1 test test      0 Aug  2 12:42 Module.symvers
		-rw-rw-r-- 1 test test   2390 Aug  2 11:47 tc3.c
		-rw-rw-r-- 1 test test 184616 Aug  2 12:42 tc3.ko
		-rw-rw-r-- 1 test test     84 Aug  2 12:42 tc3.mod
		-rw-rw-r-- 1 test test   1233 Aug  2 12:42 tc3.mod.c
		-rw-rw-r-- 1 test test 149488 Aug  2 12:42 tc3.mod.o
		-rw-rw-r-- 1 test test  36616 Aug  2 12:42 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
                [282169.096177] Inside queue_init function
		[282169.198261] Inside workqueue_func_1
		[282170.218283] Inside workqueue_func_1
		[282171.242140] Inside workqueue_func_1
		[282172.266278] Inside workqueue_func_1
		[282173.290254] Inside workqueue_func_1
		[282174.314224] Inside workqueue_func_1
		[282175.338284] Inside workqueue_func_1
		[282176.362292] Inside workqueue_func_1
		[282177.386297] Inside workqueue_func_1
		[282178.410281] Inside workqueue_func_1
		[282179.434217] Inside workqueue_func_2
		[282180.458275] Inside workqueue_func_2
		[282181.482260] Inside workqueue_func_2
		[282182.506300] Inside workqueue_func_2
		[282183.530275] Inside workqueue_func_2
		[282184.554217] Inside workqueue_func_2
		[282185.578258] Inside workqueue_func_2
		[282186.602256] Inside workqueue_func_2
		[282187.626266] Inside workqueue_func_2
		[282188.650265] 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
                [282192.532346] Inside queue_exit function
                [282192.532350] Destroying workqueue

.. _destroy_work_57:

.. tab-set::

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

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

        .. _destroy_work_58:

        .. 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>

        .. _destroy_work_59:

        .. 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 flush_rcu_work");

        .. _destroy_work_60:

        .. tab-set::

            .. tab-item:: Initializing work

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

                .. code-block:: c

                        INIT_RCU_WORK(&my_work,workqueue_func);

        .. _destroy_work_61:

        .. 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(1000);
                                }
                        }

        .. _destroy_work_62:

        .. tab-set::

            .. tab-item:: Queue Start Function

                * This function creates workqueue, intiializes work and queues to the workqueue.

                .. code-block:: c

                        void queue_start(void)
                        {
                                my_workqueue = create_workqueue(WQ_NAME);
                                INIT_RCU_WORK(&my_work,workqueue_func);
                                queue_rcu_work(my_workqueue,&my_work);
                        }

        .. _destroy_work_63:

        .. 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;
                        }

        .. _destroy_work_64:

        .. 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");
                                flush_rcu_work(&my_work);
                                flush_workqueue(my_workqueue);
                        }

        .. _destroy_work_65:

        .. 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;
                        }

        .. _destroy_work_66:

        .. 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);

.. _destroy_work_67:

.. tab-set::

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

        .. tab-set::

            .. tab-item:: tc4.c
                
                .. literalinclude:: destroy_work/flush_rcu_work/tc4.c
	            :language: c
        	    :linenos:

.. _destroy_work_68:

.. tab-set::

    .. tab-item:: Makefile

	.. literalinclude:: destroy_work/flush_rcu_work/Makefile
		:language: c
		:linenos:

.. _destroy_work_69:

.. 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 380
		-rw-rw-r-- 1 test test    151 Aug  2 11:47 Makefile
		-rw-rw-r-- 1 test test     80 Aug  2 12:46 modules.order
		-rw-rw-r-- 1 test test      0 Aug  2 12:46 Module.symvers
		-rw-rw-r-- 1 test test   1715 Aug  2 11:47 tc4.c
		-rw-rw-r-- 1 test test 180448 Aug  2 12:46 tc4.ko
		-rw-rw-r-- 1 test test     80 Aug  2 12:46 tc4.mod
		-rw-rw-r-- 1 test test   1104 Aug  2 12:46 tc4.mod.c
		-rw-rw-r-- 1 test test 149288 Aug  2 12:46 tc4.mod.o
		-rw-rw-r-- 1 test test  32624 Aug  2 12:46 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
                [282424.157821] Inside queue_init function
		[282424.202296] Inside workqueue_func
		[282425.226337] Inside workqueue_func
		[282426.250143] Inside workqueue_func
		[282427.274333] Inside workqueue_func
		[282428.298179] Inside workqueue_func
		[282429.322313] Inside workqueue_func
		[282430.346329] Inside workqueue_func
		[282431.370333] Inside workqueue_func
		[282432.394338] Inside workqueue_func
		[282433.418338] Inside workqueue_func
 
        * 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
                [282439.203573] Inside queue_exit function
                [282439.203578] Destroying workqueue