[visit-developers] VisIt and Qt signals

Brad Whitlock bjw at ilight.com
Tue Jun 16 16:39:03 EDT 2015


Hi Sveta,
    I made a change to RemoteProcess on the trunk that reinstalls the old
handler for SIGCHLD, if one exists.

Brad




On Tue, Jun 16, 2015 at 12:58 PM, Sveta <sveta at txcorp.com> wrote:

> Hi Brad,
> Not sure what you mean by reinstalling the old signal handler...  I see
> one more type of the signal call:  signal(SIGCHLD, DeadChildHandler).
> Should I use DeadChildHandler instead catch_dead_child and call it in Open
> after LaunchRemote?
>
> Thanks,
> Sveta
>
> On 6/16/15 10:29 AM, Brad Whitlock wrote:
>
>> Okay, it seems like the next step would be for RemoteProcess to
>> reinstall the old signal handler after it has launched the remote
>> process. That would probably clear up launching the vis and getting the
>> finished signal.
>>
>> Brad
>>
>> On Tue, Jun 16, 2015 at 7:18 AM, sveta <sveta at txcorp.com
>> <mailto:sveta at txcorp.com>> wrote:
>>
>>     Very interesting.  I commented out all signal() there and now the
>>     viz does not open at all, but the "finished" signal gets delivered.
>>     I will report more later.  Thank you, Brad!
>>     Sveta
>>
>>     On 6/15/15 3:19 PM, Brad Whitlock wrote:
>>
>>         Hi Sveta,
>>              DelayedMethods are queued up for later execution while the
>>         Methods
>>         object applies immediately. Calling DelayedMethods is useful
>>         when you
>>         want to queue up some work from a Qt slot that would take a long
>>         time to
>>         execute and would be best done from the main event loop. Both
>>         ways will
>>         get to the OpenDatabase action which will start the mdserver and
>>         engine
>>         via the RemoteProcess class I mentioned last time. I would try
>>         commenting out the calls to signal() in RemoteProcess to see if
>> that
>>         class is the culprit.
>>
>>         Brad
>>
>>
>>         On Mon, Jun 15, 2015 at 1:53 PM, Sveta <sveta at txcorp.com
>>         <mailto:sveta at txcorp.com>
>>         <mailto:sveta at txcorp.com <mailto:sveta at txcorp.com>>> wrote:
>>
>>              Hi Brad,
>>              I investigated and the problem occurs when we call
>>              VisItViewer::DelayedMethods::OpenDatabase...   What is the
>> main
>>              difference between DelayedMethods and Methods?
>>              Thank you,
>>
>>              iSveta
>>
>>              On Jun 12, 2015, at 4:52 PM, Brad Whitlock <bjw at ilight.com
>>         <mailto:bjw at ilight.com>
>>              <mailto:bjw at ilight.com <mailto:bjw at ilight.com>>> wrote:
>>
>>                  Hi Sveta,
>>                     VisIt's src/common/comm/RemoteProcess class installs
>>             a signal
>>                  handler for SIGCHLD that lets it detect when child
>>             processes die.
>>                  This is so it can detect when VisIt programs die on
>>             startup. It
>>                  looks like it does not restore any previously existing
>>             signal
>>                  handler. Maybe this is interfering with Qt's "finished"
>>             mechanism.
>>
>>                  HTH,
>>                  Brad
>>
>>
>>                  On Fri, Jun 12, 2015 at 3:30 PM, Sveta
>>             <sveta at txcorp.com <mailto:sveta at txcorp.com>
>>                  <mailto:sveta at txcorp.com <mailto:sveta at txcorp.com>>>
>> wrote:
>>
>>                      Hi everybody,
>>
>>                      We have been having a strange problem.  We have Qt
>>             process(es)
>>                      started by our application and we connect to it
>> signal
>>                      "finished."  All signals emit and all works before
>>             we load
>>                      files into VisIt.  Once we do this, the processes
>>             do not emit
>>                      "finished" (looks like).  Any ideas, suggestions
>>             and opinions
>>                      are appreciated.
>>
>>                      Best,
>>                      Sveta
>>
>>
>>
>>
>>
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