[jira] [Created] (TS-4612) In UnixNetVConnection::mainEvent should not do e->schedule_in for dummy event callback

["Oknet Xu (JIRA)" <ji...@apache.org>]

Oknet Xu created TS-4612:
----------------------------

             Summary: In UnixNetVConnection::mainEvent should not do e->schedule_in for dummy event callback 
                 Key: TS-4612
                 URL: https://issues.apache.org/jira/browse/TS-4612
             Project: Traffic Server
          Issue Type: Bug
          Components: Cop
            Reporter: Oknet Xu


NetHandler has a method: _close_vc ， It is called by InactivityCop.

first, create a dummy Event in stack,
then call UnixNetVConnection::mainEvent by vc->handleEvent(EVENT_IMMEDIATE, &event);

the handleEvent is mainEvent here.

In the UnixNetVConnection::mainEvent code:

```
int
UnixNetVConnection::mainEvent(int event, Event *e)
{
  ink_assert(event == EVENT_IMMEDIATE || event == EVENT_INTERVAL);
  ink_assert(thread == this_ethread());

  MUTEX_TRY_LOCK(hlock, get_NetHandler(thread)->mutex, e->ethread);
  MUTEX_TRY_LOCK(rlock, read.vio.mutex ? read.vio.mutex : e->ethread->mutex, e->ethread);
  MUTEX_TRY_LOCK(wlock, write.vio.mutex ? write.vio.mutex : e->ethread->mutex, e->ethread);

  if (!hlock.is_locked() || !rlock.is_locked() || !wlock.is_locked() ||
      (read.vio.mutex && rlock.get_mutex() != read.vio.mutex.get()) ||
      (write.vio.mutex && wlock.get_mutex() != write.vio.mutex.get())) {
#ifdef INACTIVITY_TIMEOUT
    if (e == active_timeout)
#endif
      e->schedule_in(HRTIME_MSECONDS(net_retry_delay));
    return EVENT_CONT;
  }
```

the dummy Event would be schedule_in into Event System by e->schedule_in(HRTIME_MSECONDS(net_retry_delay));

I think we should move the schedule_in into the INACTIVITY_TIMEOUT macro.

```
#ifdef INACTIVITY_TIMEOUT
    if (e == active_timeout)
      e->schedule_in(HRTIME_MSECONDS(net_retry_delay));
#endif
```

I'm try to allocate a Event instead dummy Event, but meet Event System callback on a deallocated UnixNetVConnection.

due to NetHandler called close_UnixNetVConnection before Event System callback the Event by schedule_in.

In NetHandler::_close_vc, depend the return value (EVENT_DONE or EVENT_CONT) from UnixNetVConnection::mainEvent, to do ++handle_event; or not.

```
    if (vc->handleEvent(EVENT_IMMEDIATE, &event) == EVENT_DONE)
      ++handle_event;
```

the 3 MUTEX_TRY_LOCK not always success on InactivityCop callback,
due to the mutex of ServerSessionVC may different from ClientSessionVC.

Only mutex of ServerSession is set to HttpSM when HttpSM pick up a Server Session from SessionPool. ServerSessionVC still keep the old mutex.



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