queue-4.4/add-hlist_add_tail_rcu-merge-git-git.kernel.org-pub-scm-linux-kernel-git-davem-net.patch

   1 From 1602f49b58abcb0d34a5f0a29d68e7c1769547aa Mon Sep 17 00:00:00 2001
   2 From: "David S. Miller" <davem@davemloft.net>
   3 Date: Sat, 23 Apr 2016 18:26:24 -0400
   4 Subject: Add hlist_add_tail_rcu() (Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net)
   5
   6 From: David S. Miller <davem@davemloft.net>
   7
   8 commit 1602f49b58abcb0d34a5f0a29d68e7c1769547aa upstream.
   9
  10 [This commit was a merge, but it added hlist_add_tail_rcu(), which is what we
  11  need in this stable tree, so I've changed the subject to be more descriptive
  12  - gregkh]
  13
  14 Signed-off-by: David S. Miller <davem@davemloft.net>
  15 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  16
  17 ---
  18  include/linux/rculist.h |   36 ++++++++++++++++++++++++++++++++++++
  19  1 file changed, 36 insertions(+)
  20
  21 --- a/include/linux/rculist.h
  22 +++ b/include/linux/rculist.h
  23 @@ -402,6 +402,42 @@ static inline void hlist_add_head_rcu(st
  24  }
  25
  26  /**
  27 + * hlist_add_tail_rcu
  28 + * @n: the element to add to the hash list.
  29 + * @h: the list to add to.
  30 + *
  31 + * Description:
  32 + * Adds the specified element to the specified hlist,
  33 + * while permitting racing traversals.
  34 + *
  35 + * The caller must take whatever precautions are necessary
  36 + * (such as holding appropriate locks) to avoid racing
  37 + * with another list-mutation primitive, such as hlist_add_head_rcu()
  38 + * or hlist_del_rcu(), running on this same list.
  39 + * However, it is perfectly legal to run concurrently with
  40 + * the _rcu list-traversal primitives, such as
  41 + * hlist_for_each_entry_rcu(), used to prevent memory-consistency
  42 + * problems on Alpha CPUs.  Regardless of the type of CPU, the
  43 + * list-traversal primitive must be guarded by rcu_read_lock().
  44 + */
  45 +static inline void hlist_add_tail_rcu(struct hlist_node *n,
  46 +                                     struct hlist_head *h)
  47 +{
  48 +       struct hlist_node *i, *last = NULL;
  49 +
  50 +       for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i))
  51 +               last = i;
  52 +
  53 +       if (last) {
  54 +               n->next = last->next;
  55 +               n->pprev = &last->next;
  56 +               rcu_assign_pointer(hlist_next_rcu(last), n);
  57 +       } else {
  58 +               hlist_add_head_rcu(n, h);
  59 +       }
  60 +}
  61 +
  62 +/**
  63   * hlist_add_before_rcu
  64   * @n: the new element to add to the hash list.
  65   * @next: the existing element to add the new element before.