fix the ret value by which we can stop benchmark in event

src/lua/internal/sysbench.lua

@@ -26,13 +26,12 @@ bool sb_more_events(int thread_id);
 -- Main event loop. This is a Lua version of sysbench.c:thread_run()
 -- ----------------------------------------------------------------------
 function thread_run(thread_id)
-   local success, ret
-
    while ffi.C.sb_more_events(thread_id) do
       ffi.C.sb_event_start(thread_id)
 
+      local success, ret
       repeat
-         local success, ret = pcall(event, thread_id)
+         success, ret = pcall(event, thread_id)
 
          if not success then
             if type(ret) ~= "table" or
@@ -43,7 +42,7 @@ function thread_run(thread_id)
          end
       until success
 
-      -- Stop the benchmark if event() returns a non-nil value
+      -- Stop the benchmark if event() returns a value other than nil or false
       if ret then
          break
       end

tests/t/api_basic.t

@@ -101,3 +101,45 @@ Error handling
   $ sysbench $SB_ARGS run
   FATAL: cannot find the event() function in *api_basic.lua (glob)
   [1]
+
+########################################################################
+event() return values
+########################################################################
+
+  $ cat >$CRAMTMP/api_basic.lua <<EOF
+  > sysbench.cmdline.options = { param = {"param", 0} }
+  > function event()
+  >   i = (i or 0) + 1
+  >   local param = sysbench.opt.param
+  >   print(i)
+  >   if param == 1 then
+  >     return 0
+  >   elseif param == 2 then
+  >     return 1
+  >   elseif param == 3 then
+  >     return true
+  >   elseif param == 4 then
+  >     return {}
+  >   elseif param == 5 then
+  >     return false
+  >   elseif param == 6 then
+  >     return nil
+  >   else
+  >     error("Unknown param value")
+  >   end
+  > end
+  > EOF
+  $ sysbench $SB_ARGS run --param=1
+  1
+  $ sysbench $SB_ARGS run --param=2
+  1
+  $ sysbench $SB_ARGS run --param=3
+  1
+  $ sysbench $SB_ARGS run --param=4
+  1
+  $ sysbench $SB_ARGS run --param=5
+  1
+  2
+  $ sysbench $SB_ARGS run --param=6
+  1
+  2