Questions tagged [os-kernel]

Questions about the fundamental component of an operating system, which manages the allocation of resources to applications.

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32
votes
2answers
43k views

What is the difference between user-level threads and kernel-level threads?

After reading several sources I'm still confused about user- and kernel-level threads. In particular: Threads can exist at both the user level and the kernel level What is the difference between ...
22
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1answer
2k views

Can an interrupt handler be preempted?

Can a running interrupt handler be pre-empted by another interrupt handler? If this is possible, in which scenarios is this safe, and in which scenarios is it not? If this is not possible, why?
14
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2answers
8k views

Performance of microkernel vs monolithic kernel

A microkernel implements all drivers as user-space programs, and implements core features like IPC in the kernel itself. A monolithic kernel, however, implements the drivers as a part of the kernel (e....
14
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2answers
119 views

What are potential pitfalls with having a minimal kernel that runs managed code?

Suppose I want to build an operating system based on a very small native lower kernel that acts as a managed code interpreter/runtime and a larger upper kernel compiled to a non-native machine ...
13
votes
3answers
1k views

How does the processor find kernel code after an interrupt?

When an interrupt occurs, the processor preempts the current process and calls kernel code to handle the interrupt. How does the processor know where to enter the kernel? I understand that there are ...
13
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1answer
3k views

Are all system calls blocking?

I was reading an article that describes the switch between user-space and kernel-space that happens upon a system call. The article says An application expects the completion of the system call ...
12
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1answer
3k views

What is the purpose of M:N (Hybrid) threading?

In other words, what advantages does Hybrid threading have over 1:1 (kernel only) and N:1 (user only) threading? This is a follow-up to What is the difference between user-level threads and kernel-...
9
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2answers
603 views

What is a file?

I'm looking for a formal definition of file that does not only include storage but also abstractions like procfs or /dev/null (or any fuse-based file) that do not relate to storage. So far I know ...
8
votes
1answer
1k views

Writing a multitasking operating system for a processor without MMU

I've been thinking of writing a hobby operating system for some of the ARM processors. There are many popular single-board computers with ARM MPU, so I simply wanted to purchase one of those (choosing ...
7
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2answers
3k views

Microsoft Singularity : why closed [closed]

I'm talking about this one research project: but MS closed it in 2008. I've read many articles about it, about high perfomance (30+% faster against tradinional monolithic kernels), much more secure ...
7
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1answer
2k views

Difference between hypervisor and exokernel

An hypervisor (1st type) is a software that creates and run virtual machines, managing guest's operative systems's requests to the hardware. An exokernel is an operative system kernel, that let's ...
6
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1answer
3k views

What is the real advantage of Google's new Fuchsia operating system kernel?

Google's new in-production OS which it desires to replace not only Android but many other devices utilizes a completely new kernel: The code differs from Android and Chrome OS due to its being ...
5
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1answer
331 views

What is the difference between a module in a monolithic kernel and a server in a microkernel?

I´m not exactly sure what kind of impact these two things have on kernel design. Are servers more flexible because of running in user space, for instance, and does adding a module require a new build ...
5
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3answers
884 views

Why do we try to maximize Lagrangian in SVMs?

I was learning about support vector machines from MIT OpenCourseWare. I figured it out. I understand why we try to minimize $\frac{1}{2} w^2$. I just did not get why we try to maximize Lagrange ...
4
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2answers
96 views

Why operating system needs interrupt stack, if it has process control block?

I'm reading about an operating system but some concept confuses me. What doesn't confuse me: When an interrupt or system call or processor exception occurs, it happens when user mode tries to ...
4
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0answers
270 views

Are these modern operating systems monolithic or microkernel?

I know that (at least at its conception) Linux and Mac OS were both monolithic kernels. My question is, what kind of kernels are Linux, Mac OS, and Windows today and why?
3
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1answer
2k views

What is a student process?

According to Galvin and Silberschatz, 5 queues are maintained in multilevel queue scheduling, each for: System Process Interactive Process Interactive Editing Process Batch process Student Process ...
3
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2answers
955 views

Dangerous interrupts

Let's say we have a fictional operating system in the user mode. Whenever an interrupt or a trap occurs, the os would switch to the Kernel mode jumping to the address determined from the interrupt ...
3
votes
1answer
39 views

Relation between Signals and Events

There are POSIX signals (linux man), and various event-based operating systems (such as TinyOS, most seem to be targeted at embedded systems). But the mechanisms seem very similar. Are the terms '...
3
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1answer
165 views

Session Memory in the Windows Kernel

While reading the paper Effective Data-Race Detection for the Kernel by John Erickson and Madanlal Musuvathi. I was stuck on a slightly tricky sentence. "Similarly, a range of kernel-address space, ...
2
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2answers
1k views

Is there a shell between the kernel and hardware

First and foremost, i know what a shell, kernel is. Now the dilemma. Today i had my systems viva in college. The examiner asked me is there a shell between the hardware and the kernel. Obviously, i ...
2
votes
1answer
2k views

User level threads are transparent to the kernel?

Find whether given statement True or False? Explain. User level threads are transparent to the kernel? My attempt : False. Since, user level threads are managed by a user level library however, ...
2
votes
2answers
332 views

Language that system calls are implemented in

Lately, I have been reading about operating systems design. The idea that all user space programs utilize Kernel services via a "System Call Interface" have got me thinking further into this. Is ...
1
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1answer
155 views

Are Time-sharing and multi-tasking operating systems same or different

My question is regarding time-sharing and multi-tasking systems. Time-sharing operating system assigns time slot to each task while multi-tasking OS runs various jobs in parallel. But as I get it, ...
1
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2answers
48 views

Are Kernel Codes (which are written in C) compiled during boot time?

I have a confusion regarding how the Kernel is loaded during the boot time. The intuition I have is like following: During installation of an OS, the compiled Code of the Kernel (depending on the ...
1
vote
1answer
19 views

Are process-safe mutexes shared between OSes?

I understand you can use process wide mutexes, but does this still apply if you have an additional virtualized operating system provisioned? For example, take two OSes: ...
1
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2answers
2k views

Switching between user-level and kernel-level threads

After reading difference between user-level threads and kernel-level threads ,now I am in doubt of context switching.Context switching is managed by OS when switching between processes/threads but ...
1
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2answers
78 views

Handling TOCTTOU with system calls

What are some of the best practices when implementing system call functionality for handling/avoiding "Time of check to time of use" (TOCTTOU) security issues?
1
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1answer
62 views

In a kernel, what are “global constructors”?

I am a beginner developing kernels (though I have developed several Hello World programs in C and C++). I frequently see reference being made to global constructors (e.g., osdev https://wiki.osdev.org/...
1
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0answers
18 views

User-level threads and information available to the kernel

User-level threads are transparent to the kernel. How is htop able to show user-level threads running on my system? I know that those threads are user-level threads ...
1
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0answers
292 views

Do user level threads take advantage of multi processing?

I asked this question here on stackoverflow, but maybe because of off-topic over there, it didn't received proper response. Does user level threads take advantage of multiprocessing ? I read one such ...
1
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0answers
23 views

local addresses in segmentation

I'm reading "Understanding Linux Kernel 3rd edition" and it starts talking about memory segments. It says that a logical address is: Included in the machine language instructions to specify the ...
0
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1answer
126 views

If I write code in machine language, then I have access to the CPU in both modes (user and kernel), since the OS is bypassed, correct?

Codes written in machine language can have access to both CPU modes (Kernel and user), since the OS is bypassed, correct?
0
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1answer
319 views

What features should a critical section have to maximize performance?

Critical sections limit performance by constraining parallel execution and adding overhead. What features should a critical section have for improving performance?
0
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1answer
31 views

Is OS mode required for accessing general purpose registers

In which of the following cases a process executing in user model is required to enter into the OS mode? (a) Decreasing the value of unsigned integer value in a register to less than 0 (b) Accessing ...
0
votes
2answers
131 views

On what abstraction is a filesystem actually built on?

Data is read in terms of a block from a storage device(magnetic, optical, flash). Size of the block depends upon the filesystem and os. The physical device may have different units of storage like ...
0
votes
1answer
84 views

How many bits are needed? Advantages/disatvantages of this configuration?

So the question is: Assume we had 15 CPU instructions and, for each instruction, we were trusting one particular component of the kernel to handle it. How many modes do we need to support (including ...
0
votes
1answer
164 views

Is my understanding of kernels correct?

System: Application OS: Scheduler, VMM, IPC, FS Drivers, dispatchers, VFS The above would be a monolithic kernel. In a monolithic kernel all core OS functions are separate from user spaaaaaace. ...
0
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1answer
6 views

need for an example of synchronous but non periodic interrupt

I know that synchronous interrupts are interrupts that occur with a clock tick (after finishing an instruction) and I think that periodic if they happen in every n ticks of the clock. To get a better ...
0
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0answers
33 views

How can an unstable kernel write a memory dump?

I always wondered how a kernel that became unstable, e.g. due to a BSOD or a kernel panic, is able to do specific tasks. For example, if a Windows driver corrupts the stack of the kernel. It leads to ...
0
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0answers
32 views

interrupts in operating system

Normally user programs are prevented from handling I/O directly by I/O instructions in them. For CPUs having explicit I/O instructions, such I/O protection is ensured by having the I/O instruction ...
0
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0answers
14 views

Operating Systems - Why Stack Growths For a Fixed Parameter N Are Inconsistent?

I am taking an Operating Systems course and as a project, we are printing the content of the PCB of a process from task_struct of that process and its mm_struct & vm_area_struct pointers. During ...
0
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0answers
283 views

What are disadvantages of a Operating System that recognise file extensions ?

When Operating system recognise the file types It has several advantages like 1. avoid mistakes like trying to print a object file that produce garbage output but I can't think about disadvantages ...
-1
votes
1answer
35 views

how applications send tcp data to internet?

What i know is that applications create "socket"(visualized concept for high level programmers),the socket will address the ip addresses and send to internet and forward the feedback data.What i ...
-2
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0answers
37 views

If a programmer uses semaphore to synchronize multiple processes, is there any chance that there will be priority inversion?

If a programmer uses semaphore to synchronize multiple processes, is there any chance that there will be priority inversion ?
-4
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1answer
89 views

Touchpad driver missing after windows 10 installation in acer E3-111-290X [closed]

I was asked by a friend to help installing windows 10 in an acer E3-111-290X that was previously running windows 7, but after installing windows 10 the touchpad stopped working.I've tried several ...