I cannot understand I can't access GUIs in worker thread.

CUIGOCIImgStatus is a class which inherits QWidget. It also includes <ui_gociimgstatus.h> generated by qmake.

I updates by using a thread which check status of other system.
If status is changed,
I set values in member variables in CUIGOCIImgStatus to update , then I call updates().
Then paintEvent() is called.
CUIGOCIImgStatus objects is a global variable to share.
It is created by main thread but is updated by only one other threads.

Usually, this works well.

but 1 out of 10, segment fault happens.

anything wrong??