GC manages its state by two variables, unix_graph_maybe_cyclic and unix_graph_grouped, both of which are set to false in the initial state. When an AF_UNIX socket is passed to an in-flight AF_UNIX socket, unix_update_graph() sets unix_graph_maybe_cyclic to true and unix_graph_grouped to false, making the next GC invocation call unix_walk_scc() to group SCCs. Once unix_walk_scc() finishes, sockets in the same SCC are linked via vertex->scc_entry. Then, unix_graph_grouped is set to true so that the following GC invocations can skip Tarjan's algorithm and simply iterate through the list in unix_walk_scc_fast(). In addition, if we know there is at least one cyclic reference, we set unix_graph_maybe_cyclic to true so that we do not skip GC. So the state transitions as follows: (unix_graph_maybe_cyclic, unix_graph_grouped) = (false, false) -> (true, false) -> (true, true) or (false, true) ^.______________/________________/ There is no transition to the initial state where both variables are false. If we consider the initial state as grouped, we can see that the GC actually has a tristate. Let's consolidate two variables into one enum. Signed-off-by: Kuniyuki Iwashima --- net/unix/garbage.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/net/unix/garbage.c b/net/unix/garbage.c index 9f62d5097973..7528e2db1293 100644 --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -121,8 +121,13 @@ static struct unix_vertex *unix_edge_successor(struct unix_edge *edge) return edge->successor->vertex; } -static bool unix_graph_maybe_cyclic; -static bool unix_graph_grouped; +enum { + UNIX_GRAPH_NOT_CYCLIC, + UNIX_GRAPH_MAYBE_CYCLIC, + UNIX_GRAPH_CYCLIC, +}; + +static unsigned char unix_graph_state; static void unix_update_graph(struct unix_vertex *vertex) { @@ -132,8 +137,7 @@ static void unix_update_graph(struct unix_vertex *vertex) if (!vertex) return; - unix_graph_maybe_cyclic = true; - unix_graph_grouped = false; + unix_graph_state = UNIX_GRAPH_MAYBE_CYCLIC; } static LIST_HEAD(unix_unvisited_vertices); @@ -536,8 +540,7 @@ static void unix_walk_scc(struct sk_buff_head *hitlist) swap(unix_vertex_unvisited_index, unix_vertex_grouped_index); unix_graph_cyclic_sccs = cyclic_sccs; - unix_graph_maybe_cyclic = !!unix_graph_cyclic_sccs; - unix_graph_grouped = true; + unix_graph_state = cyclic_sccs ? UNIX_GRAPH_CYCLIC : UNIX_GRAPH_NOT_CYCLIC; } static void unix_walk_scc_fast(struct sk_buff_head *hitlist) @@ -570,7 +573,7 @@ static void unix_walk_scc_fast(struct sk_buff_head *hitlist) list_replace_init(&unix_visited_vertices, &unix_unvisited_vertices); unix_graph_cyclic_sccs = cyclic_sccs; - unix_graph_maybe_cyclic = !!unix_graph_cyclic_sccs; + unix_graph_state = cyclic_sccs ? UNIX_GRAPH_CYCLIC : UNIX_GRAPH_NOT_CYCLIC; } static bool gc_in_progress; @@ -582,14 +585,14 @@ static void __unix_gc(struct work_struct *work) spin_lock(&unix_gc_lock); - if (!unix_graph_maybe_cyclic) { + if (unix_graph_state == UNIX_GRAPH_NOT_CYCLIC) { spin_unlock(&unix_gc_lock); goto skip_gc; } __skb_queue_head_init(&hitlist); - if (unix_graph_grouped) + if (unix_graph_state == UNIX_GRAPH_CYCLIC) unix_walk_scc_fast(&hitlist); else unix_walk_scc(&hitlist); -- 2.52.0.rc1.455.g30608eb744-goog