From 83327c71dd35a9a4ddf1bc8e70b6a983dc282d40 Mon Sep 17 00:00:00 2001
From: Alain Zscheile <zseri.devel@ytrizja.de>
Date: Sun, 27 Nov 2022 23:12:03 +0100
Subject: [PATCH] prevent dead-lock during garbage-collection

---
 lib/floof/packet_spool.ex    | 85 +++++++++++++++---------------------
 lib/floof/session_manager.ex | 22 ++++++----
 2 files changed, 49 insertions(+), 58 deletions(-)

diff --git a/lib/floof/packet_spool.ex b/lib/floof/packet_spool.ex
index 285e6f6..cba2678 100644
--- a/lib/floof/packet_spool.ex
+++ b/lib/floof/packet_spool.ex
@@ -46,10 +46,6 @@ defmodule Floof.PacketSpool do
   @impl true
   def init(state) do
     :ok = File.mkdir_p(state)
-
-    # in 5 seconds
-    Process.send_after(self(), :collect_garbage, 5 * 1000)
-
     {:ok, state}
   end
 
@@ -134,59 +130,50 @@ defmodule Floof.PacketSpool do
   end
 
   @impl true
-  def handle_cast({:drop, hash}, state) do
-    case File.rm(hash_to_path(hash, state)) do
-      :ok -> nil
-      {:error, e} -> Logger.error("spool: unable to remove #{inspect(hash)}: #{inspect(e)}")
+  def handle_call({:collect_garbage_keep_only, to_keep}, _, state) do
+    {:ok, items} = File.ls(state)
+
+    present =
+      MapSet.new(
+        Enum.flat_map(items, fn x ->
+          case Base.url_decode64(x) do
+            {:ok, y} ->
+              [y]
+
+            {:error, e} ->
+              Logger.warn("spool: unable to decode entry name #{x}: #{inspect(e)}")
+              []
+          end
+        end)
+      )
+
+    to_keep = MapSet.new(to_keep)
+    to_remove = MapSet.difference(present, to_keep)
+
+    if not Enum.empty?(to_remove) do
+      Logger.debug("spool: to_remove #{inspect(to_remove)}")
+
+      for hash <- to_remove do
+        case File.rm(hash_to_path(hash, state)) do
+          :ok ->
+            nil
+
+          {:error, e} ->
+            Logger.error("spool: unable to remove #{inspect(hash)}: #{inspect(e)}")
+        end
+      end
     end
 
     {:noreply, state}
   end
 
   @impl true
-  def handle_info(:collect_garbage, state) do
-    case GenServer.call(Floof.SessionManager, :get_keep_only, :infinity) do
-      :error ->
-        nil
-
-      {:ok, to_keep} ->
-        {:ok, items} = File.ls(state)
-
-        present =
-          MapSet.new(
-            Enum.flat_map(items, fn x ->
-              case Base.url_decode64(x) do
-                {:ok, y} ->
-                  [y]
-
-                {:error, e} ->
-                  Logger.warn("spool: unable to decode entry name #{x}: #{inspect(e)}")
-                  []
-              end
-            end)
-          )
-
-        to_keep = MapSet.new(to_keep)
-        to_remove = MapSet.difference(present, to_keep)
-
-        if not Enum.empty?(to_remove) do
-          Logger.debug("spool: to_remove #{inspect(to_remove)}")
-
-          for hash <- to_remove do
-            case File.rm(hash_to_path(hash, state)) do
-              :ok ->
-                nil
-
-              {:error, e} ->
-                Logger.error("spool: unable to remove #{inspect(hash)}: #{inspect(e)}")
-            end
-          end
-        end
+  def handle_cast({:drop, hash}, state) do
+    case File.rm(hash_to_path(hash, state)) do
+      :ok -> nil
+      {:error, e} -> Logger.error("spool: unable to remove #{inspect(hash)}: #{inspect(e)}")
     end
 
-    # do this again in 15 seconds
-    Process.send_after(self(), :collect_garbage, 15 * 1000)
-
     {:noreply, state}
   end
 
diff --git a/lib/floof/session_manager.ex b/lib/floof/session_manager.ex
index faf9b32..ea1d269 100644
--- a/lib/floof/session_manager.ex
+++ b/lib/floof/session_manager.ex
@@ -15,6 +15,7 @@ defmodule Floof.SessionManager do
   @impl true
   def init({file, opts}) do
     {:ok, file} = :dets.open_file(file, opts ++ [type: :bag])
+    Process.send_after(self(), :collect_garbage, 5 * 1000)
     {:ok, %Floof.SessionManager{dets_file: file}}
   end
 
@@ -143,16 +144,19 @@ defmodule Floof.SessionManager do
   end
 
   @impl true
-  def handle_call(:get_keep_only, _, state) do
-    {:reply,
-     case :dets.match(state.dets_file, {'_', '$2'}) do
-       {:error, e} ->
-         Logger.error("garbage collection error: #{inspect(e)}")
-         :error
+  def handle_info(:collect_garbage, state) do
+    case :dets.match(state.dets_file, {'_', '$2'}) do
+      {:error, e} ->
+        Logger.error("garbage collection error: #{inspect(e)}")
+        Process.send_after(self(), :collect_garbage, 60 * 1000)
 
-       keys ->
-         {:ok, Enum.map(keys, fn [x] -> x end)}
-     end, state}
+      keys ->
+        to_keep = Enum.map(keys, fn [x] -> x end)
+        GenServer.call(Floof.PacketSpool, {:collect_garbage_keep_only, to_keep}, :infinity)
+        Process.send_after(self(), :collect_garbage, 15 * 1000)
+    end
+
+    {:noreply, state}
   end
 
   defp all_session_keys(state) do