From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
The debug-object double-free checks in __call_rcu() print out the
RCU callback function, which is usually sufficient to track down the
double free. However, all uses of things like queue_rcu_work() will
have the same RCU callback function (rcu_work_rcufn() in this case),
so a diagnostic message for a double queue_rcu_work() needs more than
just the callback function.
This commit therefore prints the last allocation address of the
double-freed callback when the callback is slab-allocated and sufficient
debugging is enabled. It uses the shiny new kmem_last_alloc() and
kmem_last_alloc_errstring() functions for this purpose.
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: <linux-mm@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/rcu/tree.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b6c9c49..788a072 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2957,6 +2957,8 @@ static void check_cb_ovld(struct rcu_data *rdp)
static void
__call_rcu(struct rcu_head *head, rcu_callback_t func)
{
+ void *allocaddr;
+ const char *allocerr;
unsigned long flags;
struct rcu_data *rdp;
bool was_alldone;
@@ -2970,8 +2972,14 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
* Use rcu:rcu_callback trace event to find the previous
* time callback was passed to __call_rcu().
*/
- WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pS()!!!\n",
- head, head->func);
+ allocaddr = kmem_last_alloc(head);
+ allocerr = kmem_last_alloc_errstring(allocaddr);
+ if (allocerr)
+ WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pS()!!! (%s)\n",
+ head, head->func, allocerr);
+ else
+ WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pS()!!! (Allocated at %pS)\n",
+ head, head->func, allocaddr);
WRITE_ONCE(head->func, rcu_leak_callback);
return;
}
--
2.9.5
