net/atm/ipcommon.c

   1 /* net/atm/ipcommon.c - Common items for all ways of doing IP over ATM */
   2
   3 /* Written 1996-2000 by Werner Almesberger, EPFL LRC/ICA */
   4
   5
   6 #include <linux/module.h>
   7 #include <linux/string.h>
   8 #include <linux/skbuff.h>
   9 #include <linux/netdevice.h>
  10 #include <linux/in.h>
  11 #include <linux/atmdev.h>
  12 #include <linux/atmclip.h>
  13
  14 #include "common.h"
  15 #include "ipcommon.h"
  16
  17
  18 #if 0
  19 #define DPRINTK(format,args...) printk(KERN_DEBUG format,##args)
  20 #else
  21 #define DPRINTK(format,args...)
  22 #endif
  23
  24
  25 /*
  26  * skb_migrate appends the list at "from" to "to", emptying "from" in the
  27  * process. skb_migrate is atomic with respect to all other skb operations on
  28  * "from" and "to". Note that it locks both lists at the same time, so to deal
  29  * with the lock ordering, the locks are taken in address order.
  30  *
  31  * This function should live in skbuff.c or skbuff.h.
  32  */
  33
  34
  35 void skb_migrate(struct sk_buff_head *from, struct sk_buff_head *to)
  36 {
  37         unsigned long flags;
  38         struct sk_buff *skb_from = (struct sk_buff *) from;
  39         struct sk_buff *skb_to = (struct sk_buff *) to;
  40         struct sk_buff *prev;
  41
  42         if ((unsigned long) from < (unsigned long) to) {
  43                 spin_lock_irqsave(&from->lock, flags);
  44                 spin_lock_nested(&to->lock, SINGLE_DEPTH_NESTING);
  45         } else {
  46                 spin_lock_irqsave(&to->lock, flags);
  47                 spin_lock_nested(&from->lock, SINGLE_DEPTH_NESTING);
  48         }
  49         prev = from->prev;
  50         from->next->prev = to->prev;
  51         prev->next = skb_to;
  52         to->prev->next = from->next;
  53         to->prev = from->prev;
  54         to->qlen += from->qlen;
  55         spin_unlock(&to->lock);
  56         from->prev = skb_from;
  57         from->next = skb_from;
  58         from->qlen = 0;
  59         spin_unlock_irqrestore(&from->lock, flags);
  60 }
  61
  62
  63 EXPORT_SYMBOL(skb_migrate);