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authorDan Gudmundsson <[email protected]>2016-02-03 15:22:04 +0100
committerDan Gudmundsson <[email protected]>2016-02-05 12:37:36 +0100
commit6233c5db89867fae35f69bd7b8ef94b32cec605d (patch)
tree239aa95006146dcfc75a76a491312c25a9ccec37 /lib/mnesia/src/mnesia_schema.erl
parent61ef7511c5ffae0b061d7cc45e9d564b02b891db (diff)
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mnesia: Avoid deadlock possibility in mnesia:del_table_copy schema
del_table_copy grabs a write lock in a new process in prepare_op/3 to change 'where_to_read' when a table copy is updated. When del_table_copy(schema, Node) is called all copies located on Node are deleted, and thus many locks are taken. Since this was done outside of the schema-transaction, mnesia's deadlock prevention algorithms was sidestepped and a deadlock could occur. Fix by always grabbing write-locks for all changed tabs early and in the same transaction, this might slow done the operation some but it must be done and it also cleans up the code.
Diffstat (limited to 'lib/mnesia/src/mnesia_schema.erl')
-rw-r--r--lib/mnesia/src/mnesia_schema.erl82
1 files changed, 17 insertions, 65 deletions
diff --git a/lib/mnesia/src/mnesia_schema.erl b/lib/mnesia/src/mnesia_schema.erl
index 593360415d..2acddccf6e 100644
--- a/lib/mnesia/src/mnesia_schema.erl
+++ b/lib/mnesia/src/mnesia_schema.erl
@@ -1297,6 +1297,7 @@ make_del_table_copy(Tab, Node) ->
_ ->
ensure_active(Cs),
verify_cstruct(Cs2),
+ get_tid_ts_and_lock(Tab, write),
[{op, del_table_copy, Storage, Node, vsn_cs2list(Cs2)}]
end.
@@ -1324,6 +1325,7 @@ remove_node_from_tabs([Tab|Rest], Node) ->
remove_node_from_tabs(Rest, Node)];
_Ns ->
verify_cstruct(Cs2),
+ get_tid_ts_and_lock(Tab, write),
[{op, del_table_copy, ram_copies, Node, vsn_cs2list(Cs2)}|
remove_node_from_tabs(Rest, Node)]
end
@@ -1355,6 +1357,7 @@ do_move_table(schema, _FromNode, _ToNode) ->
mnesia:abort({bad_type, schema});
do_move_table(Tab, FromNode, ToNode) when is_atom(FromNode), is_atom(ToNode) ->
TidTs = get_tid_ts_and_lock(schema, write),
+ %% get_tid_ts_and_lock(Tab, write), write locked by load_table in mnesia_loader
insert_schema_ops(TidTs, make_move_table(Tab, FromNode, ToNode));
do_move_table(Tab, FromNode, ToNode) ->
mnesia:abort({badarg, Tab, FromNode, ToNode}).
@@ -1993,28 +1996,11 @@ prepare_op(Tid, {op, add_table_copy, Storage, Node, TabDef}, _WaitFor) ->
{true, optional}
end;
-prepare_op(Tid, {op, del_table_copy, _Storage, Node, TabDef}, _WaitFor) ->
+prepare_op(_Tid, {op, del_table_copy, _Storage, Node, TabDef}, _WaitFor) ->
Cs = list2cs(TabDef),
Tab = Cs#cstruct.name,
-
- if
- %% Schema table lock is always required to run a schema op.
- %% No need to look it.
- node(Tid#tid.pid) == node(), Tab /= schema ->
- Self = self(),
- Pid = spawn_link(fun() -> lock_del_table(Tab, Node, Cs, Self) end),
- put(mnesia_lock, Pid),
- receive
- {Pid, updated} ->
- {true, optional};
- {Pid, FailReason} ->
- mnesia:abort(FailReason);
- {'EXIT', Pid, Reason} ->
- mnesia:abort(Reason)
- end;
- true ->
- {true, optional}
- end;
+ set_where_to_read(Tab, Node, Cs),
+ {true, optional};
prepare_op(_Tid, {op, change_table_copy_type, N, FromS, ToS, TabDef}, _WaitFor)
when N == node() ->
@@ -2228,46 +2214,6 @@ receive_sync(Nodes, Pids) ->
{abort, Else}
end.
-lock_del_table(Tab, NewNode, Cs0, Father) ->
- Ns = val({schema, active_replicas}),
- process_flag(trap_exit,true),
- Lock = fun() ->
- mnesia:write_lock_table(Tab),
- %% Sigh using cs record
- Set = fun(Node) ->
- [Cs] = normalize_cs([Cs0], Node),
- rpc:call(Node, ?MODULE, set_where_to_read, [Tab, NewNode, Cs])
- end,
- Res = [Set(Node) || Node <- Ns],
- Filter = fun(ok) ->
- false;
- ({badrpc, {'EXIT', {undef, _}}}) ->
- %% This will be the case we talks with elder nodes
- %% than 3.8.2, they will set where_to_read without
- %% getting a lock.
- false;
- (_) ->
- true
- end,
- case lists:filter(Filter, Res) of
- [] ->
- Father ! {self(), updated},
- %% When transaction is commited the process dies
- %% and the lock is released.
- receive _ -> ok end;
- Err ->
- Father ! {self(), {bad_commit, Err}}
- end,
- ok
- end,
- case mnesia:transaction(Lock) of
- {atomic, ok} -> ok;
- {aborted, R} -> Father ! {self(), R}
- end,
- unlink(Father),
- unlink(whereis(mnesia_tm)),
- exit(normal).
-
set_where_to_read(Tab, Node, Cs) ->
case mnesia_lib:val({Tab, where_to_read}) of
Node ->
@@ -2418,13 +2364,19 @@ undo_prepare_op(Tid, {op, add_table_copy, Storage, Node, TabDef}) ->
insert_cstruct(Tid, Cs2, true) % Don't care about the version
end;
-undo_prepare_op(_Tid, {op, del_table_copy, _, Node, TabDef})
- when Node == node() ->
- WriteLocker = get(mnesia_lock),
- WriteLocker =/= undefined andalso (WriteLocker ! die),
+undo_prepare_op(_Tid, {op, del_table_copy, _, Node, TabDef}) ->
Cs = list2cs(TabDef),
Tab = Cs#cstruct.name,
- mnesia_lib:set({Tab, where_to_read}, Node);
+ if node() =:= Node ->
+ mnesia_lib:set({Tab, where_to_read}, Node);
+ true ->
+ case mnesia_lib:val({Tab, where_to_read}) of
+ nowhere ->
+ mnesia_lib:set_remote_where_to_read(Tab);
+ true ->
+ ignore
+ end
+ end;
undo_prepare_op(_Tid, {op, change_table_copy_type, N, FromS, ToS, TabDef})
when N == node() ->