3rd-party/linux-kernel-module-cheat
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Move sleep and workqueue module doc to README

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sleep was broken because the workqueue was declared locally inside init,
further evidence that no one has ever run the examples :-(
This commit is contained in:
Ciro Santilli
2018-07-07 19:04:43 +01:00
parent 0ccbc04da0
commit 7d16a5c024
5 changed files with 89 additions and 62 deletions
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3
kernel_module/README.adoc
View File

@@ -1,7 +1,4 @@
https://github.com/cirosantilli/linux-kernel-module-cheat#directory-structure
. Asynchronous
.. link:sleep.c[]
.. link:timer.c[]
.. link:work_from_work.c[]
.. link:workqueue_cheat.c[]

42
kernel_module/sleep.c
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@@ -1,48 +1,24 @@
/*
Usage:
insmod /sleep.ko
rmmod sleep
dmesg prints an integer every second until rmmod.
Since insmod returns, this also illustrates how the work queues are asynchronous.
*/
/* https://github.com/cirosantilli/linux-kernel-module-cheat#sleep */
#include <linux/delay.h> /* usleep_range */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h> /* atomic_t */
#include <linux/workqueue.h>
static struct workqueue_struct *queue;
static atomic_t run = ATOMIC_INIT(1);
static void work_func(struct work_struct *work)
{
int i = 0;
while (atomic_read(&run)) {
pr_info("%d\n", i);
usleep_range(1000000, 1000001);
i++;
if (i == 10)
i = 0;
}
}
static u32 n = 5;
module_param(n, int, S_IRUSR | S_IWUSR);
static int myinit(void)
{
DECLARE_WORK(work, work_func);
queue = create_workqueue("myworkqueue");
queue_work(queue, &work);
u32 i;
for (i = 0; i < n; ++i) {
pr_info("%d\n", i);
usleep_range(1000000, 1000001);
}
return 0;
}
static void myexit(void)
{
atomic_set(&run, 0);
destroy_workqueue(queue);
}
static void myexit(void) {}
module_init(myinit)
module_exit(myexit)

8
kernel_module/work_from_work.c
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@@ -1,12 +1,10 @@
/*
Declare more work from a workqueue.
*/
/* https://github.com/cirosantilli/linux-kernel-module-cheat#workqueue-from-workqueue */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/workqueue.h>
static int i = 0;
static int i;
static struct workqueue_struct *queue;
static void work_func(struct work_struct *work);
@@ -18,6 +16,8 @@ static void work_func(struct work_struct *work)
{
pr_info("%d\n", i);
i++;
if (i == 10)
i = 0;
queue_delayed_work(queue, &next_work, HZ);
}

35
kernel_module/workqueue_cheat.c
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@@ -1,45 +1,38 @@
/*
Usage:
insmod /workqueue_cheat.ko
# dmesg => worker
rmmod workqueue_cheat
Creates a separate thread. So init_module can return, but some work will still get done.
Can't call this just workqueue.c because there is already a built-in with that name:
https://unix.stackexchange.com/questions/364956/how-can-insmod-fail-with-kernel-module-is-already-loaded-even-is-lsmod-does-not
Workqueues are a convenience frontend for kthreads.
Bibliography:
- https://www.ibm.com/developerworks/library/l-tasklets/
*/
/* https://github.com/cirosantilli/linux-kernel-module-cheat#workqueue */
#include <linux/delay.h> /* usleep_range */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h> /* atomic_t */
#include <linux/workqueue.h>
static struct workqueue_struct *queue;
static atomic_t run = ATOMIC_INIT(1);
static void work_func(struct work_struct *work)
{
pr_info("worker\n");
int i = 0;
while (atomic_read(&run)) {
pr_info("%d\n", i);
usleep_range(1000000, 1000001);
i++;
if (i == 10)
i = 0;
}
}
DECLARE_WORK(work, work_func);
static int myinit(void)
{
queue = create_singlethread_workqueue("myworkqueue");
queue = create_workqueue("myworkqueue");
queue_work(queue, &work);
return 0;
}
static void myexit(void)
{
/* Waits for jobs to finish. */
atomic_set(&run, 0);
destroy_workqueue(queue);
}