The following commit has been merged into the core/rcu branch of tip:
Commit-ID: b4b7914a6a73fc169fd1ce2fcd78a1d83d9528a9
Gitweb:
https://git.kernel.org/tip/b4b7914a6a73fc169fd1ce2fcd78a1d83d9528a9
Author: Paul E. McKenney <paul...@kernel.org>
AuthorDate: Tue, 08 Dec 2020 13:45:49 -08:00
Committer: Paul E. McKenney <paul...@kernel.org>
CommitterDate: Fri, 22 Jan 2021 15:24:16 -08:00
rcu: Make call_rcu() print mem_dump_obj() info for double-freed callback
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 calls mem_dump_obj() to dump out any additional
available information on the double-freed callback.
Cc: Christoph Lameter <c...@linux.com>
Cc: Pekka Enberg <penb...@kernel.org>
Cc: David Rientjes <rient...@google.com>
Cc: Joonsoo Kim <iamjoonsoo....@lge.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: <linux...@kvack.org>
Reported-by: Andrii Nakryiko <and...@kernel.org>
Tested-by: Naresh Kamboju <naresh.kamb...@linaro.org>
Signed-off-by: Paul E. McKenney <paul...@kernel.org>
---
kernel/rcu/tree.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 40e5e3d..84513c5 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2941,6 +2941,7 @@ static void check_cb_ovld(struct rcu_data *rdp)
static void
__call_rcu(struct rcu_head *head, rcu_callback_t func)
{
+ static atomic_t doublefrees;
unsigned long flags;
struct rcu_data *rdp;
bool was_alldone;
@@ -2954,8 +2955,10 @@ __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);
+ if (atomic_inc_return(&doublefrees) < 4) {
+ pr_err("%s(): Double-freed CB %p->%pS()!!! ",
__func__, head, head->func);
+ mem_dump_obj(head);
+ }
WRITE_ONCE(head->func, rcu_leak_callback);
return;
}
