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memory: unregister AddressSpace MemoryListener within BQL 

address_space_destroy_dispatch is called from an RCU callback and hence
outside the iothread mutex (BQL).  However, after address_space_destroy
no new accesses can hit the destroyed AddressSpace so it is not necessary
to observe changes to the memory map.  Move the memory_listener_unregister
call earlier, to make it thread-safe again.

Reported-by: Alex Williamson <alex.williamson@redhat.com>
Fixes: 374f2981d1
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Paolo Bonzini 2015-02-10 10:25:44 -07:00 committed by Alex Williamson
parent a2f2d288b5
commit 6e48e8f9e0
3 changed files with 7 additions and 1 deletions
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6
exec.c
View File

@ -2059,11 +2059,15 @@ void address_space_init_dispatch(AddressSpace *as)
memory_listener_register(&as->dispatch_listener, as);
}
void address_space_unregister(AddressSpace *as)
{
memory_listener_unregister(&as->dispatch_listener);
}
void address_space_destroy_dispatch(AddressSpace *as)
{
AddressSpaceDispatch *d = as->dispatch;
memory_listener_unregister(&as->dispatch_listener);
g_free(d);
as->dispatch = NULL;
}

1
include/exec/memory-internal.h
View File

@ -23,6 +23,7 @@
typedef struct AddressSpaceDispatch AddressSpaceDispatch;
void address_space_init_dispatch(AddressSpace *as);
void address_space_unregister(AddressSpace *as);
void address_space_destroy_dispatch(AddressSpace *as);
extern const MemoryRegionOps unassigned_mem_ops;

1
memory.c
View File

@ -1978,6 +1978,7 @@ void address_space_destroy(AddressSpace *as)
as->root = NULL;
memory_region_transaction_commit();
QTAILQ_REMOVE(&address_spaces, as, address_spaces_link);
address_space_unregister(as);
/* At this point, as->dispatch and as->current_map are dummy
* entries that the guest should never use. Wait for the old