lower half mask

This article is reproduced to: http://linux.cn/thread-5510-1-1.html This article mainly from the user's point of view to the Linux 2.6 kernel of the lower half of the mechanism SOFTIRQ, tasklet and Workqueue analysis, for these three mechanisms in the kernel of the implementation of the concrete does not carry out in-depth analysis, if the reader is interested to understand, You can read the relevant parts

6.1 lower half The lower half of the task is to execute the work closely related to the interrupt processing but the interrupt processing program itself does not execute. Although there are no strict rules for division between the upper half and the

Today, I will continue to read chapter 4 "the lower half and the work to be executed after the push". I wrote "Implementation of Soft Interrupt" the day before yesterday, but it was not saved. So I wrote it again today. Let's start from scratch. We usually cut the interrupt processing process into two parts or two halves. The interrupt handler is the top half (to

tasklet codes can be executed concurrently on multiple CPUs at the same time , unlike the BH mechanism, which must be strictly serialized (that is, only one CPU can perform BH functions in the system at the same time).Soft Interrupt is the argument that interrupts the lower half, the tasklet mechanism is a special example of soft interrupts, and the soft interrupt vectors HI_SOFTIRQ and TASKLET_SOFTIRQ are

First, you need to understand the concept of Interruption: An "interruption" is just a signal. When the hardware needs to get attention from the processor, it can send this signal. The kernel maintains a registry for the interrupt signal line, which is similar to the I/O port registry. The module must request an interrupt channel (or interrupt request IRQ) before using the interrupt, and then release the channel after using it. The APIs used are request_irq () and free_irq (). Note that it is

Copyright Notice: respect for the original. Reprint please retain the Source: Blog.csdn.net/shallnet, the article is only for learning exchange, do not use for commercial use " The interrupt handler executes asynchronously, which interrupts other important code, and the other interrupts at the interrupt peer are masked when it is executed, and all other interrupts on the current processor are likely to be masked out, and interrupt handlers cannot be blocked, so the interrupt processing needs t

Interrupt processing is divided into two parts: the interrupt handler is the upper half, it receives an interrupt, executes immediately, but only does the work with strict time limits, while another part called the lower half mainly does the work that is allowed to be done later. This second half is the focus of today.

"copyright notice: respect for the original, reproduced please retain the source: Blog.csdn.net/shallnet, the article is only for learning exchange, do not use for commercial use " The interrupt handler executes asynchronously, interrupting other important code, which is blocked by other interrupts at runtime, and all other interrupts on the current processor may be masked, and interrupt handlers cannot be blocked, so the interrupt processing needs to be ended as soon as possible. Due to these

" copyright notice: respect for the original, reproduced please retain the source: Blog.csdn.net/shallnet, the article is only for learning exchange, do not use for commercial path " NBSP;NBSP; tasklet is a lower-half mechanism implemented with soft interrupts. compared to soft interrupts, the Tasklet interface is more simple and convenient, and the lock protection requirements are low. Task

) source code1 void __init softirq_init (void)2{3 OPEN_SOFTIRQ ( TASKLET_SOFTIRQ, Tasklet_action, NULL); 4 Open_softirq (HI_SOFTIRQ, tasklet_hi_action, NULL); 5 }1.2.4 Tasklet is implemented through soft interrupts.HI_SOFTIRQ and TASKLET_SOFTIRQ are key to Tasklet's implementation through soft interrupts, as shown in relationship 2-1.Figure 1-1 Tasklet the connection between data structures implemented by soft interruptsThe Tasklet mechanism creates HI_SOFTIRQ or TASKLET_SOFTIRQ two types

Let's start by explaining why the kernel divides interrupts into the upper and lower partsBecause the interrupt itself interrupts normal program execution, task scheduling cannot be performed in the interrupt, so the interrupt needs to be returned quickly, but some operations must be performed in the interrupt.If the kernel needs to perform a hardware-related, time-sensitive, cannot be interrupted operation, then these operations should be placed in t

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