On 6/16/15 5:38 AM, Daniel Wagner wrote:
static int free_thread(void *arg)
+{
+ unsigned long flags;
+ struct htab_elem *l;
+
+ while (!kthread_should_stop()) {
+ spin_lock_irqsave(&elem_freelist_lock, flags);
+ while (!list_empty(&elem_freelist)) {
+ l = list_entry(elem_freelist.next,
+ struct htab_elem, list);
+ list_del(&l->list);
+ kfree(l);
that's not right, since such thread defeats rcu protection of lookup.
We need either kfree_rcu/call_rcu or synchronize_rcu.
Obviously the former is preferred that's why I'm still digging into it.
Probably a thread that does kfree_rcu would be ok, but we shouldn't
be doing it unconditionally. For all networking programs and 99%
of tracing programs the existing code is fine and I don't want to
slow it down to tackle the corner case.
Extra spin_lock just to add it to the list is also quite costly.
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