exit.c

Linux2.4.20针对三星公司的s3c2410开发板的内核改造。

/*
 *  linux/kernel/exit.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/config.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/smp_lock.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/tty.h>
#include <linux/namespace.h>
#ifdef CONFIG_BSD_PROCESS_ACCT
#include <linux/acct.h>
#endif

#include <linux/trace.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>

extern void sem_exit (void);
extern struct task_struct *child_reaper;

int getrusage(struct task_struct *, int, struct rusage *);

static void release_task(struct task_struct * p)
{
	if (p == current)
		BUG();
#ifdef CONFIG_SMP
	wait_task_inactive(p);
#endif
	atomic_dec(&p->user->processes);
	free_uid(p->user);
	unhash_process(p);

	release_thread(p);
	current->cmin_flt += p->min_flt + p->cmin_flt;
	current->cmaj_flt += p->maj_flt + p->cmaj_flt;
	current->cnswap += p->nswap + p->cnswap;
	sched_exit(p);
	p->pid = 0;
	free_task_struct(p);
}

/*
 * This checks not only the pgrp, but falls back on the pid if no
 * satisfactory pgrp is found. I dunno - gdb doesn't work correctly
 * without this...
 */
int session_of_pgrp(int pgrp)
{
	struct task_struct *p;
	int fallback;

	fallback = -1;
	read_lock(&tasklist_lock);
	for_each_task(p) {
 		if (p->session <= 0)
 			continue;
		if (p->pgrp == pgrp) {
			fallback = p->session;
			break;
		}
		if (p->pid == pgrp)
			fallback = p->session;
	}
	read_unlock(&tasklist_lock);
	return fallback;
}

/*
 * Determine if a process group is "orphaned", according to the POSIX
 * definition in 2.2.2.52.  Orphaned process groups are not to be affected
 * by terminal-generated stop signals.  Newly orphaned process groups are
 * to receive a SIGHUP and a SIGCONT.
 *
 * "I ask you, have you ever known what it is to be an orphan?"
 */
static int will_become_orphaned_pgrp(int pgrp, struct task_struct * ignored_task)
{
	struct task_struct *p;

	read_lock(&tasklist_lock);
	for_each_task(p) {
		if ((p == ignored_task) || (p->pgrp != pgrp) ||
		    (p->state == TASK_ZOMBIE) ||
		    (p->p_pptr->pid == 1))
			continue;
		if ((p->p_pptr->pgrp != pgrp) &&
		    (p->p_pptr->session == p->session)) {
			read_unlock(&tasklist_lock);
 			return 0;
		}
	}
	read_unlock(&tasklist_lock);
	return 1;	/* (sighing) "Often!" */
}

int is_orphaned_pgrp(int pgrp)
{
	return will_become_orphaned_pgrp(pgrp, 0);
}

static inline int has_stopped_jobs(int pgrp)
{
	int retval = 0;
	struct task_struct * p;

	read_lock(&tasklist_lock);
	for_each_task(p) {
		if (p->pgrp != pgrp)
			continue;
		if (p->state != TASK_STOPPED)
			continue;
		retval = 1;
		break;
	}
	read_unlock(&tasklist_lock);
	return retval;
}

/**
 * reparent_to_init() - Reparent the calling kernel thread to the init task.
 *
 * If a kernel thread is launched as a result of a system call, or if
 * it ever exits, it should generally reparent itself to init so that
 * it is correctly cleaned up on exit.
 *
 * The various task state such as scheduling policy and priority may have
 * been inherited from a user process, so we reset them to sane values here.
 *
 * NOTE that reparent_to_init() gives the caller full capabilities.
 */
void reparent_to_init(void)
{
	write_lock_irq(&tasklist_lock);

	/* Reparent to init */
	REMOVE_LINKS(current);
	current->p_pptr = child_reaper;
	current->p_opptr = child_reaper;
	SET_LINKS(current);

	/* Set the exit signal to SIGCHLD so we signal init on exit */
	current->exit_signal = SIGCHLD;

	current->ptrace = 0;
	if ((current->policy == SCHED_OTHER) && (task_nice(current) < 0))
		set_user_nice(current, 0);
	/* cpus_allowed? */
	/* rt_priority? */
	/* signals? */
	current->cap_effective = CAP_INIT_EFF_SET;
	current->cap_inheritable = CAP_INIT_INH_SET;
	current->cap_permitted = CAP_FULL_SET;
	current->keep_capabilities = 0;
	memcpy(current->rlim, init_task.rlim, sizeof(*(current->rlim)));
	current->user = INIT_USER;

	write_unlock_irq(&tasklist_lock);
}

/*
 *	Put all the gunge required to become a kernel thread without
 *	attached user resources in one place where it belongs.
 */

void daemonize(void)
{
	struct fs_struct *fs;


	/*
	 * If we were started as result of loading a module, close all of the
	 * user space pages.  We don't need them, and if we didn't close them
	 * they would be locked into memory.
	 */
	exit_mm(current);

	current->session = 1;
	current->pgrp = 1;
	current->tty = NULL;

	/* Become as one with the init task */

	exit_fs(current);	/* current->fs->count--; */
	fs = init_task.fs;
	current->fs = fs;
	atomic_inc(&fs->count);
 	exit_files(current);
	current->files = init_task.files;
	atomic_inc(&current->files->count);
}

/*
 * When we die, we re-parent all our children.
 * Try to give them to another thread in our thread
 * group, and if no such member exists, give it to
 * the global child reaper process (ie "init")
 */
static inline void forget_original_parent(struct task_struct * father)
{
	struct task_struct * p;

	read_lock(&tasklist_lock);

	for_each_task(p) {
		if (p->p_opptr == father) {
			/* We dont want people slaying init */
			p->exit_signal = SIGCHLD;
			p->self_exec_id++;

			/* Make sure we're not reparenting to ourselves */
			p->p_opptr = child_reaper;

			p->first_time_slice = 0;
			if (p->pdeath_signal) send_sig(p->pdeath_signal, p, 0);
		}
	}
	read_unlock(&tasklist_lock);
}

static inline void close_files(struct files_struct * files)
{
	int i, j;

	j = 0;
	for (;;) {
		unsigned long set;
		i = j * __NFDBITS;
		if (i >= files->max_fdset || i >= files->max_fds)
			break;
		set = files->open_fds->fds_bits[j++];
		while (set) {
			if (set & 1) {
				struct file * file = xchg(&files->fd[i], NULL);
				if (file)
					filp_close(file, files);
			}
			i++;
			set >>= 1;
			debug_lock_break(1);
			conditional_schedule();
		}
	}
}

void put_files_struct(struct files_struct *files)
{
	if (atomic_dec_and_test(&files->count)) {
		close_files(files);
		/*
		 * Free the fd and fdset arrays if we expanded them.
		 */
		if (files->fd != &files->fd_array[0])
			free_fd_array(files->fd, files->max_fds);
		if (files->max_fdset > __FD_SETSIZE) {
			free_fdset(files->open_fds, files->max_fdset);
			free_fdset(files->close_on_exec, files->max_fdset);
		}
		kmem_cache_free(files_cachep, files);
	}
}

static inline void __exit_files(struct task_struct *tsk)
{
	struct files_struct * files = tsk->files;

	if (files) {
		task_lock(tsk);
		tsk->files = NULL;
		task_unlock(tsk);
		put_files_struct(files);
	}
}

void exit_files(struct task_struct *tsk)
{
	__exit_files(tsk);
}

static inline void __put_fs_struct(struct fs_struct *fs)
{
	/* No need to hold fs->lock if we are killing it */
	if (atomic_dec_and_test(&fs->count)) {
		dput(fs->root);
		mntput(fs->rootmnt);
		dput(fs->pwd);
		mntput(fs->pwdmnt);
		if (fs->altroot) {
			dput(fs->altroot);
			mntput(fs->altrootmnt);
		}
		kmem_cache_free(fs_cachep, fs);
	}
}

void put_fs_struct(struct fs_struct *fs)
{
	__put_fs_struct(fs);
}

static inline void __exit_fs(struct task_struct *tsk)
{
	struct fs_struct * fs = tsk->fs;

	if (fs) {
		task_lock(tsk);
		tsk->fs = NULL;
		task_unlock(tsk);
		__put_fs_struct(fs);
	}
}

void exit_fs(struct task_struct *tsk)
{
	__exit_fs(tsk);
}

/*
 * We can use these to temporarily drop into
 * "lazy TLB" mode and back.
 */
struct mm_struct * start_lazy_tlb(void)
{
	struct mm_struct *mm = current->mm;