Hi Adrián, 2013/3/4 Adrián Chaves Fernández: > Hi, > > There is not much I can add to what I already posted here: > https://forum.kde.org/viewtopic.php?f=64&t=110250 > > Last Saturday I was trying to fix a test in libmediawiki. After several hours > (12, I’m ashamed to admit) the only thing I could come up is with a simple > 6-file compilable example to reproduce the issue (see the forums post). > > To sum things up, the test starts a thread that runs a QTcpServer on a > certain port, and then executes (exec()) a KJob. The job sends a request to > the server, and after processing the reply, it finishes. This procedure is > repeated in the tests several times, with different data, to check the > results. And it fails from time to time, with different combinations of data. > The error, as it runs out, is not the server reply; it’s that the server > ocasionally gets a connection from the KJob twice — while the connection is > requested from the job only once. > > In my simplified example, I just create the job and the server thread in a > loop, get the job to call the server, finally count the requests the server > got, and start again. When the server gets more than one request in a loop, I > print “WTF!”. With 10000 loops, I bet you get some WTF! just like I did. > > I’m not too experienced in Qt/C++/KDE, so I actually don’t know if the reason > is a bug in Qt, a bug in KJob, a bad implementation of the FakeServer class, > or that I just got it all wrong. I just hope any of you guys know or can > figure it out from the example provided in the forums post, and can help me > get past this. > > Thanks, > Adrian > > PS: I’ve considered not counting the server request in the test, or using a > “sleep()” function (which might solve the problem), but we all now dirty > solutions like these will eventually come back, hiding an actual bug that > does not get tested properly, or increasing the time needed to run the batery > of tests for no reason. Not to mention that those dirty solutions would > likely hunt me in my dreams!
I'm not a network expert, and I don't know what the cause of the problem is, but I noticed two things: 1. I think the access to "m_request" in FakeServer::*Request() needs to be protected by locking m_mutex. Doing that does not seem to fix the issue, but not protecting it might lead to other problems at some point. 2. The class FakeServer follows the "You're doing it wrong" pattern (it contains the line "moveToThread(this);") , see http://blog.qt.digia.com/blog/2010/06/17/youre-doing-it-wrong/ http://woboq.com/blog/qthread-you-were-not-doing-so-wrong.html This might or might not be part of the problem. Best regards, Frank >> Visit http://mail.kde.org/mailman/listinfo/kde-devel#unsub to unsubscribe <<
