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Subject[PATCH v2 -rcu dev 3/5] rcu/tree: Add support for debug_objects debugging for kfree_rcu()
Date
Make use of RCU's debug_objects debugging support
(CONFIG_DEBUG_OBJECTS_RCU_HEAD) similar to call_rcu() and other flavors.
We queue the object during the kfree_rcu() call and dequeue it during
reclaim.

Tested that enabling CONFIG_DEBUG_OBJECTS_RCU_HEAD successfully detects
double kfree_rcu() calls.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
kernel/rcu/tree.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2e1772469de9..de13805d1bd0 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2757,6 +2757,7 @@ static void kfree_rcu_work(struct work_struct *work)
for (; head; head = next) {
next = head->next;
/* Could be possible to optimize with kfree_bulk in future */
+ debug_rcu_head_unqueue(head);
__rcu_reclaim(rcu_state.name, head);
cond_resched_tasks_rcu_qs();
}
@@ -2876,6 +2877,13 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING)
return kfree_call_rcu_nobatch(head, func);

+ if (debug_rcu_head_queue(head)) {
+ /* Probable double kfree_rcu() */
+ WARN_ONCE(1, "kfree_call_rcu(): Double-freed call. rcu_head %p\n",
+ head);
+ return;
+ }
+
head->func = func;

local_irq_save(flags); /* For safely calling this_cpu_ptr(). */
--
2.23.0.187.g17f5b7556c-goog
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