linux-kernel - [TOMOYO #11 (linux-next) 03/11] Singly linked list implementation.

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Message-Id: <20081020073648.682014372@nttdata.co.jp>
Date:	Mon, 20 Oct 2008 16:34:26 +0900
From:	Kentaro Takeda <takedakn@...data.co.jp>
To:	Stephen Smalley <sds@...ho.nsa.gov>,
	James Morris <jmorris@...ei.org>,
	Chris Wright <chrisw@...s-sol.org>
Cc:	"Serge E. Hallyn" <serue@...ibm.com>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Toshiharu Harada <haradats@...data.co.jp>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: [TOMOYO #11 (linux-next) 03/11] Singly linked list implementation.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 include/linux/list1.h |   81 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

--- /dev/null
+++ linux-next/include/linux/list1.h
@@ -0,0 +1,81 @@
+#ifndef _LINUX_LIST1_H
+#define _LINUX_LIST1_H
+
+#include <linux/list.h>
+#include <linux/rcupdate.h>
+
+/*
+ * Singly linked list implementation.
+ *
+ * This list supports only two operations.
+ * (1) Append an entry to the tail of the list.
+ * (2) Read all entries starting from the head of the list.
+ *
+ * This list is designed for holding "write once, read many" entries.
+ * This list requires no locks for read operation.
+ * This list doesn't support "remove an entry from the list" operation.
+ */
+
+/* To reduce memory usage, this list doesn't use "->prev" pointer. */
+struct list1_head {
+	struct list1_head *next;
+};
+
+#define LIST1_HEAD_INIT(name) { &(name) }
+#define LIST1_HEAD(name) struct list1_head name = LIST1_HEAD_INIT(name)
+
+static inline void INIT_LIST1_HEAD(struct list1_head *list)
+{
+	list->next = list;
+}
+
+/* Reuse list_entry because it doesn't use "->prev" pointer. */
+#define list1_entry list_entry
+
+/* Reuse list_for_each_rcu because it doesn't use "->prev" pointer. */
+#define list1_for_each list_for_each_rcu
+/* Reuse list_for_each_entry_rcu because it doesn't use "->prev" pointer. */
+#define list1_for_each_entry list_for_each_entry_rcu
+
+/**
+ * list1_for_each_cookie - iterate over a list with cookie.
+ * @pos:        the &struct list1_head to use as a loop cursor.
+ * @cookie:     the &struct list1_head to use as a cookie.
+ * @head:       the head for your list.
+ *
+ * Same with list_for_each_rcu() except that this primitive uses @cookie
+ * so that we can continue iteration.
+ * @cookie must be NULL when iteration starts, and @cookie will become
+ * NULL when iteration finishes.
+ *
+ * Since list elements are never removed, we don't need to get a lock
+ * or a reference count.
+ */
+#define list1_for_each_cookie(pos, cookie, head)                      \
+	for (({ if (!cookie)                                          \
+				     cookie = head; }),               \
+	     pos = rcu_dereference((cookie)->next);                   \
+	     prefetch(pos->next), pos != (head) || ((cookie) = NULL); \
+	     (cookie) = pos, pos = rcu_dereference(pos->next))
+
+/**
+ * list1_add_tail - add a new entry to list1 list.
+ * @new: new entry to be added.
+ * @head: list head to add it before.
+ *
+ * Same with list_add_tail_rcu() without "->prev" pointer.
+ *
+ * Caller must hold a lock for protecting @head.
+ */
+static inline void list1_add_tail(struct list1_head *new,
+				  struct list1_head *head)
+{
+	struct list1_head *prev = head;
+
+	new->next = head;
+	while (prev->next != head)
+		prev = prev->next;
+	rcu_assign_pointer(prev->next, new);
+}
+
+#endif

--

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