On 21/09/17 21:51, Paolo Bonzini wrote:
> On 21/09/2017 10:50, Alexey Kardashevskiy wrote:
>> * since FlatView::rcu is used now to dispose FV, call_rcu() in
>> address_space_update_topology() is replaced with direct call to
>> flatview_unref()
>
> Hmm, this is not correct, as you could have
>
>
> thread 1 thread 2 RCU thread
> -------------------------------------------------------------
> rcu_read_lock
> read as->current_map
> set as->current_map
> flatview_unref
> '--> call_rcu
> flatview_ref
> rcu_read_unlock
> flatview_destroy
>
> I need to think a bit more about this (and possibly ask Paul...).
>
> Paolo
>
Nah, you're right, it should be like this:
diff --git a/memory.c b/memory.c
index 35b2fc5f7f..689bf53866 100644
--- a/memory.c
+++ b/memory.c
@@ -317,7 +317,7 @@ static void flatview_ref(FlatView *view)
static void flatview_unref(FlatView *view)
{
if (atomic_fetch_dec(&view->ref) == 1) {
- call_rcu(view, flatview_destroy, rcu);
+ flatview_destroy(view);
}
}
@@ -768,7 +768,7 @@ static FlatView *generate_memory_topology(MemoryRegion *mr)
flatview_simplify(view);
if (!view->nr) {
- flatview_destroy(view);
+ flatview_unref(view);
use_empty = true;
}
}
@@ -1026,7 +1026,7 @@ static void address_space_set_flatview(AddressSpace *as)
/* Writes are protected by the BQL. */
atomic_rcu_set(&as->current_map, new_view);
if (old_view) {
- flatview_unref(old_view);
+ call_rcu(view, flatview_unref, rcu);
}
--
Alexey
