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       1                 :            : /* SPDX-License-Identifier: GPL-2.0 */
       2                 :            : #ifndef _LINUX_RCULIST_BL_H
       3                 :            : #define _LINUX_RCULIST_BL_H
       4                 :            : 
       5                 :            : /*
       6                 :            :  * RCU-protected bl list version. See include/linux/list_bl.h.
       7                 :            :  */
       8                 :            : #include <linux/list_bl.h>
       9                 :            : #include <linux/rcupdate.h>
      10                 :            : 
      11                 :            : static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
      12                 :            :                                         struct hlist_bl_node *n)
      13                 :            : {
      14                 :            :         LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
      15                 :            :         LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
      16                 :            :                                                         LIST_BL_LOCKMASK);
      17                 :          3 :         rcu_assign_pointer(h->first,
      18                 :            :                 (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
      19                 :            : }
      20                 :            : 
      21                 :            : static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
      22                 :            : {
      23                 :          3 :         return (struct hlist_bl_node *)
      24                 :          3 :                 ((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
      25                 :            : }
      26                 :            : 
      27                 :            : /**
      28                 :            :  * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization
      29                 :            :  * @n: the element to delete from the hash list.
      30                 :            :  *
      31                 :            :  * Note: hlist_bl_unhashed() on the node returns true after this. It is
      32                 :            :  * useful for RCU based read lockfree traversal if the writer side
      33                 :            :  * must know if the list entry is still hashed or already unhashed.
      34                 :            :  *
      35                 :            :  * In particular, it means that we can not poison the forward pointers
      36                 :            :  * that may still be used for walking the hash list and we can only
      37                 :            :  * zero the pprev pointer so list_unhashed() will return true after
      38                 :            :  * this.
      39                 :            :  *
      40                 :            :  * The caller must take whatever precautions are necessary (such as
      41                 :            :  * holding appropriate locks) to avoid racing with another
      42                 :            :  * list-mutation primitive, such as hlist_bl_add_head_rcu() or
      43                 :            :  * hlist_bl_del_rcu(), running on this same list.  However, it is
      44                 :            :  * perfectly legal to run concurrently with the _rcu list-traversal
      45                 :            :  * primitives, such as hlist_bl_for_each_entry_rcu().
      46                 :            :  */
      47                 :            : static inline void hlist_bl_del_init_rcu(struct hlist_bl_node *n)
      48                 :            : {
      49                 :            :         if (!hlist_bl_unhashed(n)) {
      50                 :            :                 __hlist_bl_del(n);
      51                 :            :                 n->pprev = NULL;
      52                 :            :         }
      53                 :            : }
      54                 :            : 
      55                 :            : /**
      56                 :            :  * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
      57                 :            :  * @n: the element to delete from the hash list.
      58                 :            :  *
      59                 :            :  * Note: hlist_bl_unhashed() on entry does not return true after this,
      60                 :            :  * the entry is in an undefined state. It is useful for RCU based
      61                 :            :  * lockfree traversal.
      62                 :            :  *
      63                 :            :  * In particular, it means that we can not poison the forward
      64                 :            :  * pointers that may still be used for walking the hash list.
      65                 :            :  *
      66                 :            :  * The caller must take whatever precautions are necessary
      67                 :            :  * (such as holding appropriate locks) to avoid racing
      68                 :            :  * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
      69                 :            :  * or hlist_bl_del_rcu(), running on this same list.
      70                 :            :  * However, it is perfectly legal to run concurrently with
      71                 :            :  * the _rcu list-traversal primitives, such as
      72                 :            :  * hlist_bl_for_each_entry().
      73                 :            :  */
      74                 :            : static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
      75                 :            : {
      76                 :            :         __hlist_bl_del(n);
      77                 :            :         n->pprev = LIST_POISON2;
      78                 :            : }
      79                 :            : 
      80                 :            : /**
      81                 :            :  * hlist_bl_add_head_rcu
      82                 :            :  * @n: the element to add to the hash list.
      83                 :            :  * @h: the list to add to.
      84                 :            :  *
      85                 :            :  * Description:
      86                 :            :  * Adds the specified element to the specified hlist_bl,
      87                 :            :  * while permitting racing traversals.
      88                 :            :  *
      89                 :            :  * The caller must take whatever precautions are necessary
      90                 :            :  * (such as holding appropriate locks) to avoid racing
      91                 :            :  * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
      92                 :            :  * or hlist_bl_del_rcu(), running on this same list.
      93                 :            :  * However, it is perfectly legal to run concurrently with
      94                 :            :  * the _rcu list-traversal primitives, such as
      95                 :            :  * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency
      96                 :            :  * problems on Alpha CPUs.  Regardless of the type of CPU, the
      97                 :            :  * list-traversal primitive must be guarded by rcu_read_lock().
      98                 :            :  */
      99                 :            : static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
     100                 :            :                                         struct hlist_bl_head *h)
     101                 :            : {
     102                 :            :         struct hlist_bl_node *first;
     103                 :            : 
     104                 :            :         /* don't need hlist_bl_first_rcu because we're under lock */
     105                 :            :         first = hlist_bl_first(h);
     106                 :            : 
     107                 :          3 :         n->next = first;
     108                 :          3 :         if (first)
     109                 :          3 :                 first->pprev = &n->next;
     110                 :          3 :         n->pprev = &h->first;
     111                 :            : 
     112                 :            :         /* need _rcu because we can have concurrent lock free readers */
     113                 :            :         hlist_bl_set_first_rcu(h, n);
     114                 :            : }
     115                 :            : /**
     116                 :            :  * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type
     117                 :            :  * @tpos:       the type * to use as a loop cursor.
     118                 :            :  * @pos:        the &struct hlist_bl_node to use as a loop cursor.
     119                 :            :  * @head:       the head for your list.
     120                 :            :  * @member:     the name of the hlist_bl_node within the struct.
     121                 :            :  *
     122                 :            :  */
     123                 :            : #define hlist_bl_for_each_entry_rcu(tpos, pos, head, member)            \
     124                 :            :         for (pos = hlist_bl_first_rcu(head);                            \
     125                 :            :                 pos &&                                                  \
     126                 :            :                 ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
     127                 :            :                 pos = rcu_dereference_raw(pos->next))
     128                 :            : 
     129                 :            : #endif