[jira] [Commented] (TS-4614) In UnixNetVConnection::mainEvent should not do e->schedule_in for dummy event callback

["Phil Sorber (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TS-4614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15629600#comment-15629600 ] 

Phil Sorber commented on TS-4614:
---------------------------------

Please create a back port PR using the method we discussed at the Summit. My slides are on the wiki.

thanks.

> In UnixNetVConnection::mainEvent should not do e->schedule_in for dummy event callback 
> ---------------------------------------------------------------------------------------
>
>                 Key: TS-4614
>                 URL: https://issues.apache.org/jira/browse/TS-4614
>             Project: Traffic Server
>          Issue Type: Bug
>          Components: Cop
>            Reporter: Oknet Xu
>            Assignee: Oknet Xu
>             Fix For: 7.0.0
>
>          Time Spent: 1h 10m
>  Remaining Estimate: 0h
>
> 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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