执行tasklet任务的进程ID是多少？

peimichael

又看了下原帖，才发现你这个明显就是ksoftirqd的pid嘛
tasklet是在软中断基础上实现的，软中断默认是在中断上下文运行，
但是有时候（比如软中断太多，一次处理不完）会借用内核线程ksoftirqd来完成，
你这个结果没问题。
tasklet没有自己的pid的

印随

但是如果我是直接在内核模块中调度tasklet任务的时候
打印出上下文的PID是0

0有意义吗？

[ 本帖最后由 印随 于 2009-10-22 21:20 编辑 ]

peimichael

打印出0估计是因为正在cpu空闲的时候，idle进程被中断打断，然后就打印出idle的pid，
tasklet有一部分是在中断上下文进行的，如果没有使用独立中断堆栈的话，打印出谁的pid都有可能
还是猜测，不保证正确

chenda0.03

软中断的一个调度点是在do_IRQ退出的时候，因此tasklet可能运行在任何进程的内核栈上，current就是通过内核栈来取得的

fox144215

tasklet是运行在软中断之上的。

openspace

原帖由 xiaozhe2000 于 2009-10-22 14:23 发表
tasklet应该有专门的kernel thread来运行，pid=3应该是合理的的

ULK3

Checks for active (pending) softirqs should be perfomed periodically, but without inducing too much overhead. They are performed in a few points of the kernel code. Here is a list of the most significant points (be warned that number and position of the softirq checkpoints change both with the kernel version and with the supported hardware architecture):

When the kernel invokes the local_bh_enable( ) function

to enable softirqs on the local CPU

The name local_bh_enable( ) refers to a special type of deferrable function called "bottom half" that no longer exists in Linux 2.6.

When the do_IRQ( ) function finishes handling an I/O interrupt and invokes the irq_exit( ) macro

If the system uses an I/O APIC, when the smp_apic_timer_interrupt( ) function finishes handling a local timer interrupt (see the section "Timekeeping Architecture in Multiprocessor Systems" in Chapter 6)

In multiprocessor systems, when a CPU finishes handling a function triggered by a CALL_FUNCTION_VECTOR interprocessor interrupt

When one of the special ksoftirqd/n kernel threads is awakened (see later)

The ksoftirqd/n kernel threads represent a solution for a critical trade-off problem.
...

The ksoftirqd/n kernel threads try to solve this difficult trade-off problem. The do_softirq( ) function determines what softirqs are pending and executes their functions. After a few iterations, if the flow of softirqs does not stop, the function wakes up the kernel thread and terminates (step 10 of _ _do_softirq( )). The kernel thread has low priority, so user programs have a chance to run; but if the machine is idle, the pending softirqs are executed quickly.

这个不一定，应该也会在特定点上处理一些