Understanding the linux kernel-ch3-Process descriptor

最新推荐文章于 2017-03-04 00:03:08 发布

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#descriptor #linux #struct #list #thread #each

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本文深入探讨了Linux内核中的进程组织方式，包括进程结构、等待队列的工作原理及其内部实现细节。此外，还介绍了如何通过资源限制来控制进程的行为，确保系统的稳定运行。

The process list
	init_task	//i386/kernel/init_task.c
		struct task_struct init_task = INIT_TASK(init_task);

	REMOVE_LINKS		include/linux/sched.h
	SET_LINKS
		#define REMOVE_LINKS(p) do {				/
			if (thread_group_leader(p))			/
				list_del_init(&(p)->tasks);		/
			remove_parent(p);			/
			} while (0)

		#define SET_LINKS(p) do {				/
			if (thread_group_leader(p))			/
				list_add_tail(&(p)->tasks,&init_task.tasks);	/
			add_parent(p, (p)->parent);			/
			} while (0)

	for_each_process
		#define for_each_process(p) /
			for (p = &init_task ; (p = next_task(p)) != &init_task ; )

The lists of TASK_RUNNING processes
	run_list of task_struct
	array of task_struct

Relationships Among Processes
	real_parent of task_struct
	parent of task_struct
	children of task_struct
	sibling of task_struct
	group_leader of task_struct
	tgid
	：

The pidhash table and chained lists
	four hash tables
	because the process descriptor includes fields that represent different types of PID

How Processes Are Organized
	TASK_STOPPED, EXIT_ZOMBIE, or EXIT_DEAD state are not linked
	TASK_INTERRUPTIBLE or TASK_UNINTERRUPTIBLE state are
	subdivided into many classes, each of which corresponds to a specific event

	wait_queue_head_t				//include/linux/wait.h
		struct _ _wait_queue_head {
		spinlock_t lock;
		struct list_head task_list;
		};
	Element
		struct __wait_queue {
			unsigned int flags;
			struct task_struct * task;
			wait_queue_func_t func;
			struct list_head task_list;
		};
	我就像内核中等待队列中的一个要素。处在睡眠中，在等待某个事件的出现，把我唤醒。
	但是就算这个事件出现了，被唤醒的也不一定是我，因为我不一定处在队列的前头

	exclusive processes		flags == 1	排他
	exclusive processes		flags == 0	非排他

	Handling wait queues
		DECLARE_WAIT_QUEUE_HEAD(name)
		init_waitqueue_head( )
		init_waitqueue_entry(q,p )
		default_wake_function( )
		:

	void sleep_on(wait_queue_head_t *q)				//kernel/sched.c
	void interruptible_sleep_on(wait_queue_head_t *q)
	long interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
	long sleep_on_timeout(wait_queue_head_t *q, long timeout)

				//kernel/fork.c
	void prepare_to_wait(wait_queue_head_t q, wait_queue_t wait, int state)
	prepare_to_wait_exclusive(wait_queue_head_t q, wait_queue_t wait, int state)
	void finish_wait(wait_queue_head_t q, wait_queue_t wait)

	wake_up

	Process Resource Limits			//include/linux/resource.h
		struct rlimit {
			unsigned long	rlim_cur;
			unsigned long	rlim_max;
		};
		RLIM_INFINITY (0xffffffff)
	/*
	* Resource limits
	*/
#define RLIMIT_CPU		0		/* CPU time in ms */
#define RLIMIT_FSIZE		1		/* Maximum filesize */
#define RLIMIT_DATA		2		/* max data size */
#define RLIMIT_STACK		3		/* max stack size */
#define RLIMIT_CORE		4		/* max core file size */
#define RLIMIT_RSS		5		/* max resident set size */
#define RLIMIT_NPROC		6		/* max number of processes */
#define RLIMIT_NOFILE		7		/* max number of open files */
#define RLIMIT_MEMLOCK		8		/* max locked-in-memory address space */
#define RLIMIT_AS		9		/* address space limit */
#define RLIMIT_LOCKS		10		/* maximum file locks held */

#define RLIM_NLIMITS		11