Linux-Kernel-Internals

- Linux Kernel Internals: https://ankitkdev.com/blog/
- Char Driver: https://ankitkdev.com/blog/linux-kernel/device-driver/char-driver/
- fasync Method: https://ankitkdev.com/blog/linux-kernel/device-driver/fasync/
- Ioctl Interface: https://ankitkdev.com/blog/linux-kernel/device-driver/ioctl/
- Poll Method: https://ankitkdev.com/blog/linux-kernel/device-driver/poll/
- Proc-Interface: https://ankitkdev.com/blog/linux-kernel/device-driver/proc/
- Completion-Variable: https://ankitkdev.com/blog/linux-kernel/deferred-work/completion-variable/
- Tasklet: https://ankitkdev.com/blog/linux-kernel/deferred-work/tasklet/
- Timers: https://ankitkdev.com/blog/linux-kernel/deferred-work/timer/
- Wait Queue: https://ankitkdev.com/blog/linux-kernel/deferred-work/wait-queue/
- container_of(): https://ankitkdev.com/blog/linux-kernel/macros/container_of/
- Debugging Macros: https://ankitkdev.com/blog/linux-kernel/macros/debug/
- Module Parameters: https://ankitkdev.com/blog/linux-kernel/macros/kernel-module/
- pr_fmt(): https://ankitkdev.com/blog/linux-kernel/macros/pr-family/
- Stringification: https://ankitkdev.com/blog/linux-kernel/macros/string/
- Error Handling with Pointers: https://ankitkdev.com/blog/kernal-internals/error-handling/
- Kbuild Makefile: https://ankitkdev.com/blog/kernal-internals/kbuild/
- SLUB debug: https://ankitkdev.com/blog/kernel-debugging/debug-slub-memory/
- C Memory Layout: https://ankitkdev.com/blog/c/c-memory-layout/
- do { ... } while (0): https://ankitkdev.com/blog/c/do-while-loop/
- Error Handling: https://ankitkdev.com/blog/c/error-handling/
- Forward Declarations: https://ankitkdev.com/blog/c/forward-declaration-in-c/
- Return value by Macro: https://ankitkdev.com/blog/c/return-by-macro/
- unsigned :\ 0 Bit-Fields in c: https://ankitkdev.com/blog/c/zero-width-bit-field/
- Variadic Macro: https://ankitkdev.com/blog/c/variadic-macro/
- Zero Padding in C: https://ankitkdev.com/blog/c/padding/
- programming concepts: https://ankitkdev.com/blog/theory/
- Build & Install Linux Kernel for BBB: https://ankitkdev.com/blog/misc/build-linux-kernel-BBB/
- Configure U-boot for BBB: https://ankitkdev.com/blog/misc/configure-uboot-bbb/
- Install Ubuntu Server on Qemu: https://ankitkdev.com/blog/misc/install-ubuntu-server-on-qemu/
- Linux Kernel Mentorship Program: https://ankitkdev.com/blog/misc/linux-kernel-mentorship-program/
- Reverse-Engineer apk/apks files: https://ankitkdev.com/blog/misc/debug-apk/


# Tasklet

See: [embetronicx tutorial](https://embetronicx.com/tutorials/linux/device-drivers/tasklet-static-method/)

```c
#include <linux/interrupt.h>

static struct tasklet_struct tlet;
static wait_queue_head_t wait;
static int loop = 5;
static int timeout = 0;

static void print_tasklet(unsigned long data)
{
	pr_debug("invoked from tasklet\n");

	if (!loop) {
		timeout = 1;
		wake_up_interruptible(wait);
		return;
	}

	loop--;
	tasklet_schedule(tlet);
}

static int read_tasklet(struct file *filp, char __user *buf, size_t size, loff_t *f_pos)
{
	tasklet_init(tlet, jiq_print_tasklet, (unsigned long)data);

	tasklet_schedule(tlet);
	wait_event_interruptible(jiq_wait, timeout);
	return 0;
}

static struct file_operations fops = {
	.read = read_tasklet,
};

```

Here u can assume that `wait_queue_head_t` is already initilized.

`tasklet` is linked to read call, when read call is triggered, `tasklet` gets schedule. Which schedule itself in `print_tasklet` and read call sleep until `print_tasklet` triggered `loop` times and then waked up by `print_tasklet`.

## _References_

- https://embetronicx.com/tutorials/linux/device-drivers/tasklet-static-method/