LCOV - code coverage report
Current view: top level - include/linux - rculist_nulls.h (source / functions) Hit Total Coverage
Test: coverage.info Lines: 1 1 100.0 %
Date: 2017-01-25 Functions: 0 0 -

          Line data    Source code
       1             : #ifndef _LINUX_RCULIST_NULLS_H
       2             : #define _LINUX_RCULIST_NULLS_H
       3             : 
       4             : #ifdef __KERNEL__
       5             : 
       6             : /*
       7             :  * RCU-protected list version
       8             :  */
       9             : #include <linux/list_nulls.h>
      10             : #include <linux/rcupdate.h>
      11             : 
      12             : /**
      13             :  * hlist_nulls_del_init_rcu - deletes entry from hash list with re-initialization
      14             :  * @n: the element to delete from the hash list.
      15             :  *
      16             :  * Note: hlist_nulls_unhashed() on the node return true after this. It is
      17             :  * useful for RCU based read lockfree traversal if the writer side
      18             :  * must know if the list entry is still hashed or already unhashed.
      19             :  *
      20             :  * In particular, it means that we can not poison the forward pointers
      21             :  * that may still be used for walking the hash list and we can only
      22             :  * zero the pprev pointer so list_unhashed() will return true after
      23             :  * this.
      24             :  *
      25             :  * The caller must take whatever precautions are necessary (such as
      26             :  * holding appropriate locks) to avoid racing with another
      27             :  * list-mutation primitive, such as hlist_nulls_add_head_rcu() or
      28             :  * hlist_nulls_del_rcu(), running on this same list.  However, it is
      29             :  * perfectly legal to run concurrently with the _rcu list-traversal
      30             :  * primitives, such as hlist_nulls_for_each_entry_rcu().
      31             :  */
      32             : static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node *n)
      33             : {
      34             :         if (!hlist_nulls_unhashed(n)) {
      35             :                 __hlist_nulls_del(n);
      36             :                 n->pprev = NULL;
      37             :         }
      38             : }
      39             : 
      40             : /**
      41             :  * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization
      42             :  * @n: the element to delete from the hash list.
      43             :  *
      44             :  * Note: hlist_nulls_unhashed() on entry does not return true after this,
      45             :  * the entry is in an undefined state. It is useful for RCU based
      46             :  * lockfree traversal.
      47             :  *
      48             :  * In particular, it means that we can not poison the forward
      49             :  * pointers that may still be used for walking the hash list.
      50             :  *
      51             :  * The caller must take whatever precautions are necessary
      52             :  * (such as holding appropriate locks) to avoid racing
      53             :  * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()
      54             :  * or hlist_nulls_del_rcu(), running on this same list.
      55             :  * However, it is perfectly legal to run concurrently with
      56             :  * the _rcu list-traversal primitives, such as
      57             :  * hlist_nulls_for_each_entry().
      58             :  */
      59             : static inline void hlist_nulls_del_rcu(struct hlist_nulls_node *n)
      60             : {
      61             :         __hlist_nulls_del(n);
      62             :         n->pprev = LIST_POISON2;
      63             : }
      64             : 
      65             : /**
      66             :  * hlist_nulls_add_head_rcu
      67             :  * @n: the element to add to the hash list.
      68             :  * @h: the list to add to.
      69             :  *
      70             :  * Description:
      71             :  * Adds the specified element to the specified hlist_nulls,
      72             :  * while permitting racing traversals.
      73             :  *
      74             :  * The caller must take whatever precautions are necessary
      75             :  * (such as holding appropriate locks) to avoid racing
      76             :  * with another list-mutation primitive, such as hlist_nulls_add_head_rcu()
      77             :  * or hlist_nulls_del_rcu(), running on this same list.
      78             :  * However, it is perfectly legal to run concurrently with
      79             :  * the _rcu list-traversal primitives, such as
      80             :  * hlist_nulls_for_each_entry_rcu(), used to prevent memory-consistency
      81             :  * problems on Alpha CPUs.  Regardless of the type of CPU, the
      82             :  * list-traversal primitive must be guarded by rcu_read_lock().
      83             :  */
      84             : static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n,
      85             :                                         struct hlist_nulls_head *h)
      86             : {
      87             :         struct hlist_nulls_node *first = h->first;
      88             : 
      89             :         n->next = first;
      90             :         n->pprev = &h->first;
      91             :         rcu_assign_pointer(h->first, n);
      92             :         if (!is_a_nulls(first))
      93             :                 first->pprev = &n->next;
      94             : }
      95           1 : /**
      96             :  * hlist_nulls_for_each_entry_rcu - iterate over rcu list of given type
      97             :  * @tpos:       the type * to use as a loop cursor.
      98             :  * @pos:        the &struct hlist_nulls_node to use as a loop cursor.
      99             :  * @head:       the head for your list.
     100             :  * @member:     the name of the hlist_nulls_node within the struct.
     101             :  *
     102             :  */
     103             : #define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \
     104             :         for (pos = rcu_dereference((head)->first);                    \
     105             :                 (!is_a_nulls(pos)) &&                   \
     106             :                 ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \
     107             :                 pos = rcu_dereference(pos->next))
     108             : 
     109             : #endif
     110             : #endif

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