rcu: Add support for debug_objects debugging for kfree_rcu()

This commit applies RCU's debug_objects debugging to the new batched
kfree_rcu() implementations.  The object is queued at the kfree_rcu()
call and dequeued 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>
[ paulmck: Fix IRQ per kbuild test robot <lkp@intel.com> feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a40fd58..0512221 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2749,6 +2749,7 @@ static void kfree_rcu_work(struct work_struct *work)
        for (; head; head = next) {
                next = head->next;
                // Potentially optimize with kfree_bulk in future.
+               debug_rcu_head_unqueue(head);
                __rcu_reclaim(rcu_state.name, head);
                cond_resched_tasks_rcu_qs();
        }
@@ -2855,6 +2856,12 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
                spin_lock(&krcp->lock);
 
        // Queue the object but don't yet schedule the batch.
+       if (debug_rcu_head_queue(head)) {
+               // Probable double kfree_rcu(), just leak.
+               WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
+                         __func__, head);
+               goto unlock_return;
+       }
        head->func = func;
        head->next = krcp->head;
        krcp->head = head;
@@ -2866,6 +2873,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
                schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
        }
 
+unlock_return:
        if (krcp->initialized)
                spin_unlock(&krcp->lock);
        local_irq_restore(flags);