preemption

Can preemptive multitasking of native code be implemented in user space on Linux?

由 ℡╲_俬逩灬. 提交于 2019-12-21 10:16:05
问题 I'm wondering if it's possible to implement preemptive multitasking of native code within a single process in user space on Linux. (That is, externally pause some running native code, save the context, swap in a different context, and resume execution, all orchestrated by user space but using calls that may enter the kernel.) I was thinking this could be done using a signal handler for SIGALRM , and the *context() family but it turns out that the entire *context() family is async-signal

What is preemption / What is a preemtible kernel? What is it good for?

由 ♀尐吖头ヾ 提交于 2019-12-18 10:04:36
问题 Explained in your own words, what is preemption and what does it mean to a (linux) kernel? What are advantages and disadvantages in having a preemptible kernel? 回答1: Preemptive multitasking - Running several processes/threads on a single processor, creating the illusion that they run concurrently when actually each is allocated small multiplexed time slices to run in. A process is "preempted" when it is scheduled out of execution and waits for the next time slice to run in. A preemptive

What does it mean to say “linux kernel is preemptive”?

由 …衆ロ難τιáo~ 提交于 2019-12-17 18:17:15
问题 I read that Linux kernel is preemptive, which is different from most Unix kernels. So, what does it really mean for a kernal to be preemptive? Some analogies or examples would be better than pure theoretical explanation. ADD 1 -- 11:00 AM 12/7/2018 Preemptive is just one paradigm of multi-tasking. There are others like Cooperative Multi-tasking. A better understanding can be achieved by comparing them. 回答1: Imagine the simple view of preemptive multi-tasking. We have two user tasks, both of

What is an uninterruptible process?

由 落花浮王杯 提交于 2019-12-17 03:22:16
问题 Sometimes whenever I write a program in Linux and it crashes due to a bug of some sort, it will become an uninterruptible process and continue running forever until I restart my computer (even if I log out). My questions are: What causes a process to become uninterruptible? How do I stop that from happening? This is probably a dumb question, but is there any way to interrupt it without restarting my computer? 回答1: An uninterruptible process is a process which happens to be in a system call

Preemptive Kernel Design

由 隐身守侯 提交于 2019-12-13 05:14:27
问题 I've always thought kernels to be non-preemptable. That is, the kernel code runs to completion, with scheduling taking place only when returning to userspace. I am now curious about the changes need to be made when designing a preemptable kernel. My thought process so far: Say the kernel is running on behalf of some userspace process and is suddenly preempted. We store the current processor information in the process's kernel stack. We then mark the process as runnable. When that process is

How does a scheduler regain control when wanted?

由 最后都变了- 提交于 2019-12-11 19:24:57
问题 I'm reading about scheduling, but I can't figure out how a scheduler regains control after it invokes code in the user space. E.g. the scheduler passes the control to some app in the user space which does some infinite loop and no other hardware interrupt occurs on an one core chip. All documents talk about the scheduler regaining control and preemptivly interrupting the user process, but how does that work if the control is never passed back to the OS? Question: Does the scheduler register

How does a VxWorks scheduler get executed?

由 柔情痞子 提交于 2019-12-08 17:05:50
问题 Would like to know how the scheduler gets called so that it can switch tasks. As in even if its preemptive scheduling or round robin scheduling - the scheduler should come in to picture to do any kind of task switching. Supposing a low priority task has an infinite loop - when does the scheduler intervene and switch to a higher priority task? Query is: 1. Who calls the scheduler? [in VxWorks] 2. If it gets called at regular intervals - how is that mechanism implemented? Thanks in advance. -

How to save state when preempted on a Google preemptible instance?

由 此生再无相见时 提交于 2019-12-08 03:30:28
I need to be able to save the state of a Centos-based Google Compute instance when it first receives a preemption signal. The documentation very clearly indicates that a "ACPI G2 Soft Off" signal is sent 30 seconds before a preemptible shutdown. Unfortunately, Google has given no examples to demonstrate how to capture this signal and I have not yet found a way to capture it. My initial attempts have all been focused around the ACPI Interface using the acpid daemon. Using it, I have been able to capture the shutdown (button/power) event without any problems. But no matter what event I try to

How to limit the execution time of a function in C/POSIX?

由 血红的双手。 提交于 2019-12-06 05:22:51
Similar to this question , I'd like to limit the execution time of a function--preferably with microsecond accuracy--in C. I imagine that C++ exceptions could be used to achieve a result similar to this Python solution. Though it's not ideal, such an approach is wholly unavailable in plain C. I wonder, then, how might I interrupt the execution of a function after a certain time interval in C on a Posix system? For relatively simple situations a bit of silly business works just fine, but that adds a fair amount of code orthogonal to the problem solution. Let's say I have a function like so:

Why linux disables kernel preemption after the kernel code holds a spinlock?

由 时间秒杀一切 提交于 2019-12-05 00:52:59
问题 I am new to Linux and am reading Linux device drivers book by Rubini & Corbet. I am confused at one statement related to spinlocks ; the book states If a nonpreemptive uniprocessor system ever went into a spin on a lock, it would spin forever; no other thread would ever be able to obtain the CPU to release the lock. For this reason, spinlock operations on uniprocessor systems without preemption enabled are optimized to do nothing, with the exception of the ones that change the IRQ masking
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