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Subject[PATCH RFC tip/core/rcu 2/6] rcu: List-debug variants of rcu list routines.
Date
From: Dave Jones <davej@redhat.com>

* 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>
---
include/linux/rculist.h | 7 ++++++-
lib/list_debug.c | 22 ++++++++++++++++++++++
2 files changed, 28 insertions(+), 1 deletions(-)

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index d079290..a20c050 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -30,6 +30,7 @@
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
+#ifndef CONFIG_DEBUG_LIST
static inline void __list_add_rcu(struct list_head *new,
struct list_head *prev, struct list_head *next)
{
@@ -38,6 +39,10 @@ static inline void __list_add_rcu(struct list_head *new,
rcu_assign_pointer(list_next_rcu(prev), new);
next->prev = new;
}
+#else
+extern void __list_add_rcu(struct list_head *new,
+ struct list_head *prev, struct list_head *next);
+#endif

/**
* list_add_rcu - add a new entry to rcu-protected list
@@ -108,7 +113,7 @@ static inline void list_add_tail_rcu(struct list_head *new,
*/
static inline void list_del_rcu(struct list_head *entry)
{
- __list_del(entry->prev, entry->next);
+ __list_del_entry(entry);
entry->prev = LIST_POISON2;
}

diff --git a/lib/list_debug.c b/lib/list_debug.c
index 982b850..3810b48 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);
--
1.7.8


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