Improved deadlock bug test script

1 files changed, 19 insertions, 10 deletions

diff --git a/tests/deadlock.lua b/tests/deadlock.lua
index 8ccae89..655fad2 100644
--- a/tests/deadlock.lua
+++ b/tests/deadlock.lua
@@ -1,28 +1,37 @@
+-- this script tests the fix of a bug that could cause the mutex of a keeper state to remain locked
+-- see https://github.com/LuaLanes/lanes/commit/0cc1c9c9dcea5955f7dab921d9a2fff78c4e1729
+
 local lanes = require('lanes').configure()
 local linda = lanes.linda "deadlock_linda"
 
 local do_extra_stuff = true
 
 if do_extra_stuff then
-        -- just something to make send() succeed and receive() fail:
+        -- just something to make send() succeed and receive() fail (any C function exposed by some module will do)
         local payload = { lanes.require('socket').connect }
 
         -- lane generator
         local g = lanes.gen('*', function()
-                set_debug_threadname "deadlock_lane"
-                print("In lane 1:", table.unpack{pcall(linda.receive, linda, 'tmp')})
-                print("In lane 2:", table.unpack{pcall(linda.receive, linda, 'tmp')})
+                set_debug_threadname( "deadlock_lane")
+                -- wrapping inside pcall makes the Lanes module unaware that something went wrong
+                print( "In lane 1:", table.unpack{ pcall( linda.receive, linda, 'tmp')})
+                -- with the bug not fixed, and non-recursive mutexes, we can hang here
+                print( "In lane 2:", table.unpack{ pcall( linda.receive, linda, 'tmp')})
+                -- return something out of the lane
                 return 33, 55
         end)
 
-        -- send payload twice
-        linda:send('tmp', payload, payload)
+        -- send payload twice. succeeds because sending stores a function identification string in the linda's keeper state
+        linda:send( 'tmp', payload, payload)
+        -- start the lane
         local h = g()
+        -- wait for lane completion
         local err, stack = h:join()
-        print('we reach here and then deadlock', err, stack)
+        print( 'result of lane execution', err, stack)
 end
--- start lane
 
--- wait some
+-- With the bug not fixed, the linda keeper's mutex is still acquired,
+-- and the program hangs when the internal linda used for timers attempts to acquire the same keeper (there is only one by default)
+print('waiting a bit')
 lanes.sleep(2)
-print('we never reach here')
\ No newline at end of file
+print('we should reach here')
\ No newline at end of file