text: /*
   *  linux/kernel/fork.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */
  
  /*
   *  'fork.c' contains the help-routines for the 'fork' system call
   * (see also entry.S and others).
   * Fork is rather simple, once you get the hang of it, but the memory
   * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
   */
  
  #include <linux/config.h>
  #include <linux/slab.h>
  #include <linux/init.h>
  #include <linux/unistd.h>
  #include <linux/smp_lock.h>
  #include <linux/module.h>
  #include <linux/vmalloc.h>
  #include <linux/completion.h>
  #include <linux/namespace.h>
  #include <linux/personality.h>
  #include <linux/compiler.h>
  
  #include <asm/pgtable.h>
  #include <asm/pgalloc.h>
  #include <asm/uaccess.h>
  #include <asm/mmu_context.h>
  
  /* The idle threads do not count.. */
  int nr_threads;
  int nr_running;
  
  int max_threads;
  unsigned long total_forks;	/* Handle normal Linux uptimes. */
  int last_pid;
  
  struct task_struct *pidhash[PIDHASH_SZ];
  
  void add_wait_queue(wait_queue_head_t *q, wait_queue_t * wait)
  {
  	unsigned long flags;
  
  	wait->flags &= ~WQ_FLAG_EXCLUSIVE;
  	wq_write_lock_irqsave(&q->lock, flags);
  	__add_wait_queue(q, wait);
  	wq_write_unlock_irqrestore(&q->lock, flags);
  }
  
  void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t * wait)
  {
  	unsigned long flags;
  
  	wait->flags |= WQ_FLAG_EXCLUSIVE;
  	wq_write_lock_irqsave(&q->lock, flags);
  	__add_wait_queue_tail(q, wait);
  	wq_write_unlock_irqrestore(&q->lock, flags);
  }
  
  void remove_wait_queue(wait_queue_head_t *q, wait_queue_t * wait)
  {
  	unsigned long flags;
  
  	wq_write_lock_irqsave(&q->lock, flags);
  	__remove_wait_queue(q, wait);
  	wq_write_unlock_irqrestore(&q->lock, flags);
  }
  
  void __init fork_init(unsigned long mempages)
  {
  	/*
  	 * The default maximum number of threads is set to a safe
  	 * value: the thread structures can take up at most half
  	 * of memory.
  	 */
  	max_threads = mempages / (THREAD_SIZE/PAGE_SIZE) / 8;
  
  	init_task.rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
  	init_task.rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
  }
  
  /* Protects next_safe and last_pid. */
  spinlock_t lastpid_lock = SPIN_LOCK_UNLOCKED;
  
  static int get_pid(unsigned long flags)
  {
  	static int next_safe = PID_MAX;
  	struct task_struct *p;
  	int pid, beginpid;
  
  	if (flags & CLONE_PID)
  		return current->pid;
  
  	spin_lock(&lastpid_lock);
  	beginpid = last_pid;
  	if((++last_pid) & 0xffff8000) {
  		last_pid = 300;		/* Skip daemons etc. */
  		goto inside;
  	}
  	if(last_pid >= next_safe) {
  inside:
  		next_safe = PID_MAX;
  		read_lock(&tasklist_lock);
  	repeat:
  		for_each_task(p) {
  			if(p->pid == last_pid	||
  			   p->pgrp == last_pid	||
  			   p->tgid == last_pid	||
  			   p->session == last_pid) {
  				if(++last_pid >= next_safe) {
  					if(last_pid & 0xffff8000)
  						last_pid = 300;
  					next_safe = PID_MAX;
  				}
  				if(unlikely(last_pid == beginpid))
  					goto nomorepids;
  				goto repeat;
  			}
  			if(p->pid > last_pid && next_safe > p->pid)
  				next_safe = p->pid;
  			if(p->pgrp > last_pid && next_safe > p->pgrp)
  				next_safe = p->pgrp;
  			if(p->tgid > last_pid && next_safe > p->tgid)
  				next_safe = p->tgid;
  			if(p->session > last_pid && next_safe > p->session)
  				next_safe = p->session;
  		}
  		read_unlock(&tasklist_lock);
  	}
  	pid = last_pid;
  	spin_unlock(&lastpid_lock);
  
  	return pid;
  
  nomorepids:
  	read_unlock(&tasklist_lock);
  	spin_unlock(&lastpid_lock);
  	return 0;
  }
  
  static inline int dup_mmap(struct mm_struct * mm)
  {
  	struct vm_area_struct * mpnt, *tmp, **pprev;
  	int retval;
  
  	flush_cache_mm(current->mm);
  	mm->locked_vm = 0;
  	mm->mmap = NULL;
  	mm->mmap_cache = NULL;
  	mm->map_count = 0;
  	mm->rss = 0;
  	mm->cpu_vm_mask = 0;
  	mm->swap_address = 0;
  	pprev = &mm->mmap;
  
  	/*
  	 * Add it to the mmlist after the parent.
  	 * Doing it this way means that we can order the list,
  	 * and fork() won't mess up the ordering significantly.
  	 * Add it first so that swapoff can see any swap entries.
  	 */
  	spin_lock(&mmlist_lock);
  	list_add(&mm->mmlist, &current->mm->mmlist);
  	mmlist_nr++;
  	spin_unlock(&mmlist_lock);
  
  	for (mpnt = current->mm->mmap ; mpnt ; mpnt = mpnt->vm_next) {
  		struct file *file;
  
  		retval = -ENOMEM;
  		if(mpnt->vm_flags & VM_DONTCOPY)
  			continue;
  		tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
  		if (!tmp)
  			goto fail_nomem;
  		*tmp = *mpnt;
  		tmp->vm_flags &= ~VM_LOCKED;
  		tmp->vm_mm = mm;
  		tmp->vm_next = NULL;
  		file = tmp->vm_file;
  		if (file) {
  			struct inode *inode = file->f_dentry->d_inode;
  			get_file(file);
  			if (tmp->vm_flags & VM_DENYWRITE)
  				atomic_dec(&inode->i_writecount);
        
  			/* insert tmp into the share list, just after mpnt */
  			spin_lock(&inode->i_mapping->i_shared_lock);
  			if((tmp->vm_next_share = mpnt->vm_next_share) != NULL)
  				mpnt->vm_next_share->vm_pprev_share =
  					&tmp->vm_next_share;
  			mpnt->vm_next_share = tmp;
  			tmp->vm_pprev_share = &mpnt->vm_next_share;
  			spin_unlock(&inode->i_mapping->i_shared_lock);
  		}
  
  		/*
  		 * Link in the new vma and copy the page table entries:
  		 * link in first so that swapoff can see swap entries.
  		 */
  		spin_lock(&mm->page_table_lock);
  		*pprev = tmp;
  		pprev = &tmp->vm_next;
  		mm->map_count++;
  		retval = copy_page_range(mm, current->mm, tmp);
  		spin_unlock(&mm->page_table_lock);
  
  		if (tmp->vm_ops && tmp->vm_ops->open)
  			tmp->vm_ops->open(tmp);
  
  		if (retval)
  			goto fail_nomem;
  	}
  	retval = 0;
  	build_mmap_rb(mm);
  
  fail_nomem:
  	flush_tlb_mm(current->mm);
  	return retval;
  }
  
  spinlock_t mmlist_lock __cacheline_aligned = SPIN_LOCK_UNLOCKED;
  int mmlist_nr;
  
  #define allocate_mm()	(kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
  #define free_mm(mm)	(kmem_cache_free(mm_cachep, (mm)))
  
  static struct mm_struct * mm_init(struct mm_struct * mm)
  {
  	atomic_set(&mm->mm_users, 1);
  	atomic_set(&mm->mm_count, 1);
  	init_rwsem(&mm->mmap_sem);
  	mm->page_table_lock = SPIN_LOCK_UNLOCKED;
  	mm->pgd = pgd_alloc(mm);
  	mm->def_flags = 0;
  	if (mm->pgd)
  		return mm;
  	free_mm(mm);
  	return NULL;
  }
  	
  
  /*
   * Allocate and initialize an mm_struct.
   */
  struct mm_struct * mm_alloc(void)
  {
  	struct mm_struct * mm;
  
  	mm = allocate_mm();
  	if (mm) {
  		memset(mm, 0, sizeof(*mm));
  		return mm_init(mm);
  	}
  	return NULL;
  }
  
  /*
   * Called when the last reference to the mm
   * is dropped: either by a lazy thread or by
   * mmput. Free the page directory and the mm.
   */
  inline void __mmdrop(struct mm_struct *mm)
  {
  	BUG_ON(mm == &init_mm);
  	pgd_free(mm->pgd);
  	destroy_context(mm);
  	free_mm(mm);
  }
  
  /*
   * Decrement the use count and release all resources for an mm.
   */
  void mmput(struct mm_struct *mm)
  {
  	if (atomic_dec_and_lock(&mm->mm_users, &mmlist_lock)) {
  		extern struct mm_struct *swap_mm;
  		if (swap_mm == mm)
  			swap_mm = list_entry(mm->mmlist.next, struct mm_struct, mmlist);
  		list_del(&mm->mmlist);
  		mmlist_nr--;
  		spin_unlock(&mmlist_lock);
  		exit_mmap(mm);
  		mmdrop(mm);
  	}
  }
  
  /* Please note the differences between mmput and mm_release.
   * mmput is called whenever we stop holding onto a mm_struct,
   * error success whatever.
   *
   * mm_release is called after a mm_struct has been removed
   * from the current process.
   *
   * This difference is important for error handling, when we
   * only half set up a mm_struct for a new process and need to restore
   * the old one.  Because we mmput the new mm_struct before
   * restoring the old one. . .
   * Eric Biederman 10 January 1998
   */
  void mm_release(void)
  {
  	struct task_struct *tsk = current;
  	struct completion *vfork_done = tsk->vfork_done;
  
  	/* notify parent sleeping on vfork() */
  	if (vfork_done) {
  		tsk->vfork_done = NULL;
  		complete(vfork_done);
  	}
  }
  
  static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
  {
  	struct mm_struct * mm, *oldmm;
  	int retval;
  
  	tsk->min_flt = tsk->maj_flt = 0;
  	tsk->cmin_flt = tsk->cmaj_flt = 0;
  	tsk->nswap = tsk->cnswap = 0;
  
  	tsk->mm = NULL;
  	tsk->active_mm = NULL;
  
  	/*
  	 * Are we cloning a kernel thread?
  	 *
  	 * We need to steal a active VM for that..
  	 */
  	oldmm = current->mm;
  	if (!oldmm)
  		return 0;
  
  	if (clone_flags & CLONE_VM) {
  		atomic_inc(&oldmm->mm_users);
  		mm = oldmm;
  		goto good_mm;
  	}
  
  	retval = -ENOMEM;
  	mm = allocate_mm();
  	if (!mm)
  		goto fail_nomem;
  
  	/* Copy the current MM stuff.. */
  	memcpy(mm, oldmm, sizeof(*mm));
  	if (!mm_init(mm))
  		goto fail_nomem;
  
  	if (init_new_context(tsk,mm))
  		goto free_pt;
  
  	down_write(&oldmm->mmap_sem);
  	retval = dup_mmap(mm);
  	up_write(&oldmm->mmap_sem);
  
  	if (retval)
  		goto free_pt;
  
  	/*
  	 * child gets a private LDT (if there was an LDT in the parent)
  	 */
  	copy_segments(tsk, mm);
  
  good_mm:
  	tsk->mm = mm;
  	tsk->active_mm = mm;
  	return 0;
  
  free_pt:
  	mmput(mm);
  fail_nomem:
  	return retval;
  }
  
  static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
  {
  	struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
  	/* We don't need to lock fs - think why ;-) */
  	if (fs) {
  		atomic_set(&fs->count, 1);
  		fs->lock = RW_LOCK_UNLOCKED;
  		fs->umask = old->umask;
  		read_lock(&old->lock);
  		fs->rootmnt = mntget(old->rootmnt);
  		fs->root = dget(old->root);
  		fs->pwdmnt = mntget(old->pwdmnt);
  		fs->pwd = dget(old->pwd);
  		if (old->altroot) {
  			fs->altrootmnt = mntget(old->altrootmnt);
  			fs->altroot = dget(old->altroot);
  		} else {
  			fs->altrootmnt = NULL;
  			fs->altroot = NULL;
  		}	
  		read_unlock(&old->lock);
  	}
  	return fs;
  }
  
  struct fs_struct *copy_fs_struct(struct fs_struct *old)
  {
  	return __copy_fs_struct(old);
  }
  
  static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
  {
  	if (clone_flags & CLONE_FS) {
  		atomic_inc(&current->fs->count);
  		return 0;
  	}
  	tsk->fs = __copy_fs_struct(current->fs);
  	if (!tsk->fs)
  		return -1;
  	return 0;
  }
  
  static int count_open_files(struct files_struct *files, int size)
  {
  	int i;
  	
  	/* Find the last open fd */
  	for (i = size/(8*sizeof(long)); i > 0; ) {
  		if (files->open_fds->fds_bits[--i])
  			break;
  	}
  	i = (i+1) * 8 * sizeof(long);
  	return i;
  }
  
  static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
  {
  	struct files_struct *oldf, *newf;
  	struct file **old_fds, **new_fds;
  	int open_files, nfds, size, i, error = 0;
  
  	/*
  	 * A background process may not have any files ...
  	 */
  	oldf = current->files;
  	if (!oldf)
  		goto out;
  
  	if (clone_flags & CLONE_FILES) {
  		atomic_inc(&oldf->count);
  		goto out;
  	}
  
  	tsk->files = NULL;
  	error = -ENOMEM;
  	newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
  	if (!newf) 
  		goto out;
  
  	atomic_set(&newf->count, 1);
  
  	newf->file_lock	    = RW_LOCK_UNLOCKED;
  	newf->next_fd	    = 0;
  	newf->max_fds	    = NR_OPEN_DEFAULT;
  	newf->max_fdset	    = __FD_SETSIZE;
  	newf->close_on_exec = &newf->close_on_exec_init;
  	newf->open_fds	    = &newf->open_fds_init;
  	newf->fd	    = &newf->fd_array[0];
  
  	/* We don't yet have the oldf readlock, but even if the old
             fdset gets grown now, we'll only copy up to "size" fds */
  	size = oldf->max_fdset;
  	if (size > __FD_SETSIZE) {
  		newf->max_fdset = 0;
  		write_lock(&newf->file_lock);
  		error = expand_fdset(newf, size-1);
  		write_unlock(&newf->file_lock);
  		if (error)
  			goto out_release;
  	}
  	read_lock(&oldf->file_lock);
  
  	open_files = count_open_files(oldf, size);
  
  	/*
  	 * Check whether we need to allocate a larger fd array.
  	 * Note: we're not a clone task, so the open count won't
  	 * change.
  	 */
  	nfds = NR_OPEN_DEFAULT;
  	if (open_files > nfds) {
  		read_unlock(&oldf->file_lock);
  		newf->max_fds = 0;
  		write_lock(&newf->file_lock);
  		error = expand_fd_array(newf, open_files-1);
  		write_unlock(&newf->file_lock);
  		if (error) 
  			goto out_release;
  		nfds = newf->max_fds;
  		read_lock(&oldf->file_lock);
  	}
  
  	old_fds = oldf->fd;
  	new_fds = newf->fd;
  
  	memcpy(newf->open_fds->fds_bits, oldf->open_fds->fds_bits, open_files/8);
  	memcpy(newf->close_on_exec->fds_bits, oldf->close_on_exec->fds_bits, open_files/8);
  
  	for (i = open_files; i != 0; i--) {
  		struct file *f = *old_fds++;
  		if (f)
  			get_file(f);
  		*new_fds++ = f;
  	}
  	read_unlock(&oldf->file_lock);
  
  	/* compute the remainder to be cleared */
  	size = (newf->max_fds - open_files) * sizeof(struct file *);
  
  	/* This is long word aligned thus could use a optimized version */ 
  	memset(new_fds, 0, size); 
  
  	if (newf->max_fdset > open_files) {
  		int left = (newf->max_fdset-open_files)/8;
  		int start = open_files / (8 * sizeof(unsigned long));
  		
  		memset(&newf->open_fds->fds_bits[start], 0, left);
  		memset(&newf->close_on_exec->fds_bits[start], 0, left);
  	}
  
  	tsk->files = newf;
  	error = 0;
  out:
  	return error;
  
  out_release:
  	free_fdset (newf->close_on_exec, newf->max_fdset);
  	free_fdset (newf->open_fds, newf->max_fdset);
  	kmem_cache_free(files_cachep, newf);
  	goto out;
  }
  
  static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
  {
  	struct signal_struct *sig;
  
  	if (clone_flags & CLONE_SIGHAND) {
  		atomic_inc(&current->sig->count);
  		return 0;
  	}
  	sig = kmem_cache_alloc(sigact_cachep, GFP_KERNEL);
  	tsk->sig = sig;
  	if (!sig)
  		return -1;
  	spin_lock_init(&sig->siglock);
  	atomic_set(&sig->count, 1);
  	memcpy(tsk->sig->action, current->sig->action, sizeof(tsk->sig->action));
  	return 0;
  }
  
  static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
  {
  	unsigned long new_flags = p->flags;
  
  	new_flags &= ~(PF_SUPERPRIV | PF_USEDFPU);
  	new_flags |= PF_FORKNOEXEC;
  	if (!(clone_flags & CLONE_PTRACE))
  		p->ptrace = 0;
  	p->flags = new_flags;
  }
  
  /*
   *  Ok, this is the main fork-routine. It copies the system process
   * information (task[nr]) and sets up the necessary registers. It also
   * copies the data segment in its entirety.  The "stack_start" and
   * "stack_top" arguments are simply passed along to the platform
   * specific copy_thread() routine.  Most platforms ignore stack_top.
   * For an example that's using stack_top, see
   * arch/ia64/kernel/process.c.
   */
  int do_fork(unsigned long clone_flags, unsigned long stack_start,
  	    struct pt_regs *regs, unsigned long stack_size)
  {
  	int retval;
  	struct task_struct *p;
  	struct completion vfork;
  
  	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
  		return -EINVAL;
  
  	retval = -EPERM;
  
  	/* 
  	 * CLONE_PID is only allowed for the initial SMP swapper
  	 * calls
  	 */
  	if (clone_flags & CLONE_PID) {
  		if (current->pid)
  			goto fork_out;
  	}
  
  	retval = -ENOMEM;
  	p = alloc_task_struct();
  	if (!p)
  		goto fork_out;
  
  	*p = *current;
  
  	retval = -EAGAIN;
  	/*
  	 * Check if we are over our maximum process limit, but be sure to
  	 * exclude root. This is needed to make it possible for login and
  	 * friends to set the per-user process limit to something lower
  	 * than the amount of processes root is running. -- Rik
  	 */
  	if (atomic_read(&p->user->processes) >= p->rlim[RLIMIT_NPROC].rlim_cur
  	              && !capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE))
  		goto bad_fork_free;
  
  	atomic_inc(&p->user->__count);
  	atomic_inc(&p->user->processes);
  
  	/*
  	 * Counter increases are protected by
  	 * the kernel lock so nr_threads can't
  	 * increase under us (but it may decrease).
  	 */
  	if (nr_threads >= max_threads)
  		goto bad_fork_cleanup_count;
  	
  	get_exec_domain(p->exec_domain);
  
  	if (p->binfmt && p->binfmt->module)
  		__MOD_INC_USE_COUNT(p->binfmt->module);
  
  	p->did_exec = 0;
  	p->swappable = 0;
  	p->state = TASK_UNINTERRUPTIBLE;
  
  	copy_flags(clone_flags, p);
  	p->pid = get_pid(clone_flags);
  	if (p->pid == 0 && current->pid != 0)
  		goto bad_fork_cleanup;
  
  	p->run_list.next = NULL;
  	p->run_list.prev = NULL;
  
  	p->p_cptr = NULL;
  	init_waitqueue_head(&p->wait_chldexit);
  	p->vfork_done = NULL;
  	if (clone_flags & CLONE_VFORK) {
  		p->vfork_done = &vfork;
  		init_completion(&vfork);
  	}
  	spin_lock_init(&p->alloc_lock);
  
  	p->sigpending = 0;
  	init_sigpending(&p->pending);
  
  	p->it_real_value = p->it_virt_value = p->it_prof_value = 0;
  	p->it_real_incr = p->it_virt_incr = p->it_prof_incr = 0;
  	init_timer(&p->real_timer);
  	p->real_timer.data = (unsigned long) p;
  
  	p->leader = 0;		/* session leadership doesn't inherit */
  	p->tty_old_pgrp = 0;
  	p->times.tms_utime = p->times.tms_stime = 0;
  	p->times.tms_cutime = p->times.tms_cstime = 0;
  	p->tickets = 8; //For Lottery
  	p->last_time = jiffies; //For Lottery
  	p->used_bit = 0;
  #ifdef CONFIG_SMP
  	{
  		int i;
  		p->cpus_runnable = ~0UL;
  		p->processor = current->processor;
  		/* ?? should we just memset this ?? */
  		for(i = 0; i < smp_num_cpus; i++)
  			p->per_cpu_utime[i] = p->per_cpu_stime[i] = 0;
  		spin_lock_init(&p->sigmask_lock);
  	}
  #endif
  	p->lock_depth = -1;		/* -1 = no lock */
  	p->start_time = jiffies;
  
  	INIT_LIST_HEAD(&p->local_pages);
  
  	retval = -ENOMEM;
  	/* copy all the process information */
  	if (copy_files(clone_flags, p))
  		goto bad_fork_cleanup;
  	if (copy_fs(clone_flags, p))
  		goto bad_fork_cleanup_files;
  	if (copy_sighand(clone_flags, p))
  		goto bad_fork_cleanup_fs;
  	if (copy_mm(clone_flags, p))
  		goto bad_fork_cleanup_sighand;
  	if (copy_namespace(clone_flags, p))
  		goto bad_fork_cleanup_mm;
  	retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
  	if (retval)
  		goto bad_fork_cleanup_namespace;
  	p->semundo = NULL;
  	
  	/* Our parent execution domain becomes current domain
  	   These must match for thread signalling to apply */
  	   
  	p->parent_exec_id = p->self_exec_id;
  
  	/* ok, now we should be set up.. */
  	p->swappable = 1;
  	p->exit_signal = clone_flags & CSIGNAL;
  	p->pdeath_signal = 0;
  
  	/*
  	 * "share" dynamic priority between parent and child, thus the
  	 * total amount of dynamic priorities in the system doesn't change,
  	 * more scheduling fairness. This is only important in the first
  	 * timeslice, on the long run the scheduling behaviour is unchanged.
  	 */
  	p->counter = (current->counter + 1) >> 1;
  	current->counter >>= 1;
  	if (!current->counter)
  		current->need_resched = 1;
  
  	/*
  	 * Ok, add it to the run-queues and make it
  	 * visible to the rest of the system.
  	 *
  	 * Let it rip!
  	 */
  	retval = p->pid;
  	p->tgid = retval;
  	INIT_LIST_HEAD(&p->thread_group);
  
  	/* Need tasklist lock for parent etc handling! */
  	write_lock_irq(&tasklist_lock);
  
  	/* CLONE_PARENT re-uses the old parent */
  	p->p_opptr = current->p_opptr;
  	p->p_pptr = current->p_pptr;
  	if (!(clone_flags & CLONE_PARENT)) {
  		p->p_opptr = current;
  		if (!(p->ptrace & PT_PTRACED))
  			p->p_pptr = current;
  	}
  
  	if (clone_flags & CLONE_THREAD) {
  		p->tgid = current->tgid;
  		list_add(&p->thread_group, &current->thread_group);
  	}
  
  	SET_LINKS(p);
  	hash_pid(p);
  	nr_threads++;
  	write_unlock_irq(&tasklist_lock);
  
  	if (p->ptrace & PT_PTRACED)
  		send_sig(SIGSTOP, p, 1);
  
  	wake_up_process(p);		/* do this last */
  	++total_forks;
  	if (clone_flags & CLONE_VFORK)
  		wait_for_completion(&vfork);
  
  fork_out:
  	return retval;
  
  bad_fork_cleanup_namespace:
  	exit_namespace(p);
  bad_fork_cleanup_mm:
  	exit_mm(p);
  bad_fork_cleanup_sighand:
  	exit_sighand(p);
  bad_fork_cleanup_fs:
  	exit_fs(p); /* blocking */
  bad_fork_cleanup_files:
  	exit_files(p); /* blocking */
  bad_fork_cleanup:
  	put_exec_domain(p->exec_domain);
  	if (p->binfmt && p->binfmt->module)
  		__MOD_DEC_USE_COUNT(p->binfmt->module);
  bad_fork_cleanup_count:
  	atomic_dec(&p->user->processes);
  	free_uid(p->user);
  bad_fork_free:
  	free_task_struct(p);
  	goto fork_out;
  }
  
  /* SLAB cache for signal_struct structures (tsk->sig) */
  kmem_cache_t *sigact_cachep;
  
  /* SLAB cache for files_struct structures (tsk->files) */
  kmem_cache_t *files_cachep;
  
  /* SLAB cache for fs_struct structures (tsk->fs) */
  kmem_cache_t *fs_cachep;
  
  /* SLAB cache for vm_area_struct structures */
  kmem_cache_t *vm_area_cachep;
  
  /* SLAB cache for mm_struct structures (tsk->mm) */
  kmem_cache_t *mm_cachep;
  
  void __init proc_caches_init(void)
  {
  	sigact_cachep = kmem_cache_create("signal_act",
  			sizeof(struct signal_struct), 0,
  			SLAB_HWCACHE_ALIGN, NULL, NULL);
  	if (!sigact_cachep)
  		panic("Cannot create signal action SLAB cache");
  
  	files_cachep = kmem_cache_create("files_cache", 
  			 sizeof(struct files_struct), 0, 
  			 SLAB_HWCACHE_ALIGN, NULL, NULL);
  	if (!files_cachep) 
  		panic("Cannot create files SLAB cache");
  
  	fs_cachep = kmem_cache_create("fs_cache", 
  			 sizeof(struct fs_struct), 0, 
  			 SLAB_HWCACHE_ALIGN, NULL, NULL);
  	if (!fs_cachep) 
  		panic("Cannot create fs_struct SLAB cache");
   
  	vm_area_cachep = kmem_cache_create("vm_area_struct",
  			sizeof(struct vm_area_struct), 0,
  			SLAB_HWCACHE_ALIGN, NULL, NULL);
  	if(!vm_area_cachep)
  		panic("vma_init: Cannot alloc vm_area_struct SLAB cache");
  
  	mm_cachep = kmem_cache_create("mm_struct",
  			sizeof(struct mm_struct), 0,
  			SLAB_HWCACHE_ALIGN, NULL, NULL);
  	if(!mm_cachep)
  		panic("vma_init: Cannot alloc mm_struct SLAB cache");
  }
  