What is bottom half and top half?

The so-called top half is the routine that actually responds to the interrupt—the one you register with request_irq. The bottom half is a routine that is scheduled by the top half to be executed later, at a safer time.

Can interrupt handler be interrupted?

However, such kernel control paths may be arbitrarily nested; an interrupt handler may be interrupted by another interrupt handler, thus giving raise to a nested execution of kernel threads.

Why is IRQ threaded?

The main aim of the threaded IRQ is to reduce the time spent with interrupts being disabled and that will increase the chances of handling other interrupts. In this case, interrupts have not been disabled for more time. So, we will respond to other interrupts too.

What is threaded interrupt?

An interrupt is an indication to a thread that it should stop what it is doing and do something else. It’s up to the programmer to decide exactly how a thread responds to an interrupt, but it is very common for the thread to terminate.

How are interrupts handled?

Interrupts are generally called signals which are generated by the software or hardware when a particular event or process requires immediate attention. Thus, whenever an interruption occurs the processor finishes the current instruction execution and starts the execution of the interrupt known as interrupt handling.

How do I interrupt a thread in C++?

When you want to interrupt a thread, you simply write synchronously to this variable, and then you join the thread.

Which state Cannot be interrupted OS?

An uninterruptible process is a process which happens to be in a system call (kernel function) that cannot be interrupted by a signal.

What is difference between Tasklet and Workqueue?

A tasklet always runs in the interrupt context, that means when a tasklet executes it is as if the processor is executing an interrupt service routine. On the other hand a workqueue executes as a normal process and not a interrupt, hence a worqueue can go to sleep it can hold semaphores.

What is the purpose of the top half of the interrupt?

This setup permits the top half to service a new interrupt while the bottom half is still working.

What is the top half of a Linux interrupt handler?

Linux (along with many other systems) resolves this problem by splitting the interrupt handler into two halves. The so-called top half is the routine that actually responds to the interrupt—the one you register with request_irq. The bottom half is a routine that is scheduled by the top half to be executed later,…

What are the different types of bottom half mechanisms?

3 different bottom halves mechanisms exist: Softirqs, which run in interrupt context Tasklet, which are built on top of softirqs and, therefore, run in interrupt context Work queues, which are the only bottom half mechanism run in process context

What is the difference between the top half and bottom half?

The bottom half is a routine that is scheduled by the top half to be executed later, at a safer time. The big difference between the top-half handler and the bottom half is that all interrupts are enabled during execution of the bottom half—that’s why it runs at a safer time.