kernel_thread 返回值问题

2011-02-23 04:38:23 260 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

WPF起步(中) --- 的main thread跟render thread如何通信接下来的问题是，WPF如何通知这个worker thread什么时候应该Render，这个thread跟main thread是如何通信的。要回答这个问题，我的做法是:1. 选择一个非常简单的WPF程序，观察该程序idle状态时候每个thread的状态2. 在Render thread上设定断点，当Render thread触发的时候，再次检查各个thread的状态。于是我做了一个只有简单阅读详情

int id=kernel_thread(int (*fn)(void *),...);
如果fn所指向的函数指针执行失败，那么kernel_thread是执行成功还是失败呢？
在正常情况下id应该是大于0的，但是如果fn所指向的函数指针执行失败了，那么id的返回值是怎么样的呢？

...全文

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Wenxy1 2011-02-24

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返回的是负值,错误码:



/*

 *  Ok, this is the main fork-routine.

 *

 * It copies the process, and if successful kick-starts

 * it and waits for it to finish using the VM if required.

 */

long do_fork(unsigned long clone_flags,

	      unsigned long stack_start,

	      struct pt_regs *regs,

	      unsigned long stack_size,

	      int __user *parent_tidptr,

	      int __user *child_tidptr)

{

	struct task_struct *p;

	int trace = 0;

	long nr;



	/*

	 * Do some preliminary argument and permissions checking before we

	 * actually start allocating stuff

	 */

	if (clone_flags & CLONE_NEWUSER) {

		if (clone_flags & CLONE_THREAD)

			return -EINVAL;

		/* hopefully this check will go away when userns support is

		 * complete

		 */

		if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||

				!capable(CAP_SETGID))

			return -EPERM;

	}



	/*

	 * We hope to recycle these flags after 2.6.26

	 */

	if (unlikely(clone_flags & CLONE_STOPPED)) {

		static int __read_mostly count = 100;



		if (count > 0 && printk_ratelimit()) {

			char comm[TASK_COMM_LEN];



			count--;

			printk(KERN_INFO "fork(): process `%s' used deprecated "

					"clone flags 0x%lx\n",

				get_task_comm(comm, current),

				clone_flags & CLONE_STOPPED);

		}

	}



	/*

	 * When called from kernel_thread, don't do user tracing stuff.

	 */

	if (likely(user_mode(regs)))

		trace = tracehook_prepare_clone(clone_flags);



	p = copy_process(clone_flags, stack_start, regs, stack_size,

			 child_tidptr, NULL, trace);

	/*

	 * Do this prior waking up the new thread - the thread pointer

	 * might get invalid after that point, if the thread exits quickly.

	 */

	if (!IS_ERR(p)) {

		struct completion vfork;



		trace_sched_process_fork(current, p);



		nr = task_pid_vnr(p);



		if (clone_flags & CLONE_PARENT_SETTID)

			put_user(nr, parent_tidptr);



		if (clone_flags & CLONE_VFORK) {

			p->vfork_done = &vfork;

			init_completion(&vfork);

		}



		audit_finish_fork(p);

		tracehook_report_clone(regs, clone_flags, nr, p);



		/*

		 * We set PF_STARTING at creation in case tracing wants to

		 * use this to distinguish a fully live task from one that

		 * hasn't gotten to tracehook_report_clone() yet.  Now we

		 * clear it and set the child going.

		 */

		p->flags &= ~PF_STARTING;



		if (unlikely(clone_flags & CLONE_STOPPED)) {

			/*

			 * We'll start up with an immediate SIGSTOP.

			 */

			sigaddset(&p->pending.signal, SIGSTOP);

			set_tsk_thread_flag(p, TIF_SIGPENDING);

			__set_task_state(p, TASK_STOPPED);

		} else {

			wake_up_new_task(p, clone_flags);

		}



		tracehook_report_clone_complete(trace, regs,

						clone_flags, nr, p);



		if (clone_flags & CLONE_VFORK) {

			freezer_do_not_count();

			wait_for_completion(&vfork);

			freezer_count();

			tracehook_report_vfork_done(p, nr);

		}

	} else {

		nr = PTR_ERR(p);

	}

	return nr;

}





#ifndef _ASM_GENERIC_ERRNO_BASE_H

#define _ASM_GENERIC_ERRNO_BASE_H



#define	EPERM		 1	/* Operation not permitted */

#define	ENOENT		 2	/* No such file or directory */

#define	ESRCH		 3	/* No such process */

#define	EINTR		 4	/* Interrupted system call */

#define	EIO		 5	/* I/O error */

#define	ENXIO		 6	/* No such device or address */

#define	E2BIG		 7	/* Argument list too long */

#define	ENOEXEC		 8	/* Exec format error */

#define	EBADF		 9	/* Bad file number */

#define	ECHILD		10	/* No child processes */

#define	EAGAIN		11	/* Try again */

#define	ENOMEM		12	/* Out of memory */

#define	EACCES		13	/* Permission denied */

#define	EFAULT		14	/* Bad address */

#define	ENOTBLK		15	/* Block device required */

#define	EBUSY		16	/* Device or resource busy */

#define	EEXIST		17	/* File exists */

#define	EXDEV		18	/* Cross-device link */

#define	ENODEV		19	/* No such device */

#define	ENOTDIR		20	/* Not a directory */

#define	EISDIR		21	/* Is a directory */

#define	EINVAL		22	/* Invalid argument */

#define	ENFILE		23	/* File table overflow */

#define	EMFILE		24	/* Too many open files */

#define	ENOTTY		25	/* Not a typewriter */

#define	ETXTBSY		26	/* Text file busy */

#define	EFBIG		27	/* File too large */

#define	ENOSPC		28	/* No space left on device */

#define	ESPIPE		29	/* Illegal seek */

#define	EROFS		30	/* Read-only file system */

#define	EMLINK		31	/* Too many links */

#define	EPIPE		32	/* Broken pipe */

#define	EDOM		33	/* Math argument out of domain of func */

#define	ERANGE		34	/* Math result not representable */

nuoshueihe 2011-02-24

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但是我觉得kernel_thread中的fn所执向的函数指针执行失败，并不表示这个线程创建失败啊。

yong_f 2011-02-24

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如果fn所指向的函数指针执行失败，那么kernel_thread是执行成功还是失败呢？---当然是执行失败。

leeyiqun 2011-02-23

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如果fn所指向的函数指针执行失败，那么kernel_thread是执行成功还是失败呢？---当然是执行失败。

kernel_thread 返回值问题

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