[Interest] Long pause with 5.7

[william.crocker at analog.com]

>>
>> I am porting my app to Qt 5.7
>> When I run it, it appears on the screen,
>> but there is a long pause (~10 secs.) before it is responsive.
>> I ran it with strace and there is a point where it makes
>> 100K calls to the poll() function, which accounts for the long pause.
>> I tried running it in a debugger, but the app does not exhibit the pause in
>> that context.
>
> Sounds like a threading race condition and running in the debugger changes the
> timing just enough.
>

Gave the debugger another try. On some occasions, it would
take the long pause. (The pause is more like 5 seconds.)
If I interrupt it, this is the stack trace.
Note that it is in the call to show() which precedes
my call to exec().

Bill

#0  0x0000003b0a0df113 in poll () from /lib64/libc.so.6
#1  0x0000003b0bc449f9 in ?? () from /lib64/libglib-2.0.so.0
#2  0x0000003b0bc44e4c in g_main_context_iteration () from /lib64/libglib-2.0.so.0
#3  0x00007ffff55b2740 in 
QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
    from 
/nobackup/whc/qt/5.7.0-shared-debug-64Bit-RH6-NoOpenGL/qtbase/lib/libQt5Core.so.5
#4  0x00007ffff5565229 in 
QCoreApplication::processEvents(QFlags<QEventLoop::ProcessEventsFlag>, int) ()
    from 
/nobackup/whc/qt/5.7.0-shared-debug-64Bit-RH6-NoOpenGL/qtbase/lib/libQt5Core.so.5
#5  0x000000000098c60b in MyProg::show (this=0x7fffffffb8d0) at prog.cpp:562
#6  0x0000000000986551 in MyMain (argc=@0x7fffffffc15c: 1, argv=0x7fffffffc2f8) 
at prog.cpp:151
#7  0x0000000000986ad9 in main (argc=1, argv=0x7fffffffc2f8) at yoda.cpp:221