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Subject[PATCH tip/core/rcu 5/7] rcu: Add support for debug_objects debugging for kfree_rcu()
Date
From: "Joel Fernandes (Google)" <joel@joelfernandes.org>

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>
---
kernel/rcu/tree.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a40fd58..0512221 100644
--- 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);
--
2.9.5
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