Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.4 094/131] Add hlist_add_tail_rcu() (Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net)
Date:   Mon,  1 Apr 2019 19:02:44 +0200
Message-Id: <20190401170059.818827375@linuxfoundation.org>
In-Reply-To: <20190401170051.645954551@linuxfoundation.org>
References: <20190401170051.645954551@linuxfoundation.org>
User-Agent: quilt/0.65
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David S. Miller <davem@davemloft.net>

commit 1602f49b58abcb0d34a5f0a29d68e7c1769547aa upstream.

[This commit was a merge, but it added hlist_add_tail_rcu(), which is what we
 need in this stable tree, so I've changed the subject to be more descriptive
 - gregkh]

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 include/linux/rculist.h |   36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -402,6 +402,42 @@ static inline void hlist_add_head_rcu(st
 }
 
 /**
+ * hlist_add_tail_rcu
+ * @n: the element to add to the hash list.
+ * @h: the list to add to.
+ *
+ * Description:
+ * Adds the specified element to the specified hlist,
+ * while permitting racing traversals.
+ *
+ * The caller must take whatever precautions are necessary
+ * (such as holding appropriate locks) to avoid racing
+ * with another list-mutation primitive, such as hlist_add_head_rcu()
+ * or hlist_del_rcu(), running on this same list.
+ * However, it is perfectly legal to run concurrently with
+ * the _rcu list-traversal primitives, such as
+ * hlist_for_each_entry_rcu(), used to prevent memory-consistency
+ * problems on Alpha CPUs.  Regardless of the type of CPU, the
+ * list-traversal primitive must be guarded by rcu_read_lock().
+ */
+static inline void hlist_add_tail_rcu(struct hlist_node *n,
+				      struct hlist_head *h)
+{
+	struct hlist_node *i, *last = NULL;
+
+	for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i))
+		last = i;
+
+	if (last) {
+		n->next = last->next;
+		n->pprev = &last->next;
+		rcu_assign_pointer(hlist_next_rcu(last), n);
+	} else {
+		hlist_add_head_rcu(n, h);
+	}
+}
+
+/**
  * hlist_add_before_rcu
  * @n: the new element to add to the hash list.
  * @next: the existing element to add the new element before.