Possible bug in task_wakeup() impacts Lua tasks

[Adis Nezirovic]

Hello guys,

After this commit:

  commit 0194897e540cec67d7d1e9281648b70efe403f08
  Author: Emeric Brun <eb...@haproxy.com>
  Date:   Thu Mar 30 15:37:25 2017 +0200

      MAJOR: task: task scheduler rework.

basic Lua tasks don't work anymore.
e.g. this only gets called once:

  function cron()
      while true do
          core.Debug("Hello from Cron")
          core.sleep(1)
      end
  end
  core.register_task(cron)

----

The current code in task_wakeup() checks for TASK_RUNNING and decides
that it won't call __task_wakeup(), but when Lua task wakes up, it has
both, TASK_WOKEN_TIMER and TASK_RUNNING set.

My quick fix/workaround was to add an additional check:

  if (unlikely(!(t->state & TASK_WOKEN_TIMER) &&
               (t->state & TASK_RUNNING)))

But I might be missing something more fundamental (i.e. this is really
necessary for multithreaded stuff), maybe we need additional flags when
running task_wakeup from task handlers or threads.


Best regards,
Adis