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1. ps -elf 的结果中最后面一栏，如果CMD是用[ ] 包含起来的就为内核线程，如[ksoftirqd/1]等
2. 嗯，内核线程只运行在内核态，与普通的进程无关。
3. 使用函数kernel_thread创建新的内核线程。
ULK上面讲到：
3.4.2. Kernel Threads
Traditional Unix systems delegate some critical tasks to intermittently running processes, including flushing disk caches, swapping out unused pages, servicing network connections, and so on. Indeed, it is not efficient to perform these tasks in strict linear fashion; both their functions and the end user processes get better response if they are scheduled in the background. Because some of the system processes run only in Kernel Mode, modern operating systems delegate their functions to kernel threads , which are not encumbered with the unnecessary User Mode context. In Linux, kernel threads differ from regular processes in the following ways:
Kernel threads run only in Kernel Mode, while regular processes run alternatively in Kernel Mode and in User Mode.
Because kernel threads run only in Kernel Mode, they use only linear addresses greater than PAGE_OFFSET. Regular processes, on the other hand, use all four gigabytes of linear addresses, in either User Mode or Kernel Mode.
3.4.2.1. Creating a kernel thread
The kernel_thread( ) function creates a new kernel thread. It receives as parameters the address of the kernel function to be executed (fn), the argument to be passed to that function (arg), and a set of clone flags (flags). The function essentially invokes do_fork( ) as follows:
do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, pregs, 0, NULL, NULL);
The CLONE_VM flag avoids the duplication of the page tables of the calling process: this duplication would be a waste of time and memory, because the new kernel thread will not access the User Mode address space anyway. The CLONE_UNTRACED flag ensures that no process will be able to trace the new kernel thread, even if the calling process is being traced.
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发表于 2009-02-11 11:17
发表于 2009-02-11 11:50
