rcu: List-debug variants of rcu list routines.

* Make __list_add_rcu check the next->prev and prev->next pointers
  just like __list_add does.
* Make list_del_rcu use __list_del_entry, which does the same checking
  at deletion time.

Has been running for a week here without anything being tripped up,
but it seems worth adding for completeness just in case something
ever does corrupt those lists.

Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/lib/list_debug.c b/lib/list_debug.c
index 982b850d4e7a..3810b481f940 100644
--- a/lib/list_debug.c
+++ b/lib/list_debug.c
@@ -10,6 +10,7 @@
 #include <linux/list.h>
 #include <linux/bug.h>
 #include <linux/kernel.h>
+#include <linux/rculist.h>
 
 /*
  * Insert a new entry between two known consecutive entries.
@@ -75,3 +76,24 @@ void list_del(struct list_head *entry)
         entry->prev = LIST_POISON2;
 }
 EXPORT_SYMBOL(list_del);
+
+/*
+ * RCU variants.
+ */
+void __list_add_rcu(struct list_head *new,
+                    struct list_head *prev, struct list_head *next)
+{
+        WARN(next->prev != prev,
+                "list_add_rcu corruption. next->prev should be "
+                "prev (%p), but was %p. (next=%p).\n",
+                prev, next->prev, next);
+        WARN(prev->next != next,
+                "list_add_rcu corruption. prev->next should be "
+                "next (%p), but was %p. (prev=%p).\n",
+                next, prev->next, prev);
+        new->next = next;
+        new->prev = prev;
+        rcu_assign_pointer(list_next_rcu(prev), new);
+        next->prev = new;
+}
+EXPORT_SYMBOL(__list_add_rcu);