I have seen that my Delphi app has more than one thread - 7 more exactly. OF COURSE I am not creating my own threads and I am only using 'classic' VCL controls. The program is idle. It just displays the main form. No dialogs are active, no personal/Indy/etc threads running.
Wasn't supposed to have just one thread (the VCL main thread)?
How do I know which of these (already running threads) is the main thread?
Note 1: This is related to Program freezes but the CPU utilization is zero
Note 2: I just realized that 2 or 3 of those threads are from the debugger (extra threads appear when I pause the program and invoke the 'CPU view' window).
As you see in the comments an answer to the first part of your question is broad. Just creating a new 'VCL Forms Application' project in Delphi XE7 and running it I had 4 Threads in the 'Thread Status' view. Others have mentioned TThreadedQueue, file dialogs, VCL hint code and more as a source for unaccounted threads.
For the second part of your question I suggested naming the main thread at startup with something like:
TThread.NameThreadForDebugging('Main Thread', MainThreadID);
As you mention in the comments you might not be able to name it beforehand, so in an existing debug session you could do it ad hoc:
Invoke the Evaluate / Modify window
Ctrl+F7 or
Context Menu > Debug > Evaluate / Modify
Type in MainThreadID as expression to eveluate, resulting in the ID you are looking for.
If you want you can use the context menu entry 'Name Thread' in the Thread view to name the thread with that ID.
Identifying other threads with the IDE is possible, too. A double click on a thread in the Threads view will open the current call stack. Skimming over that you might already be able to tell if this is a native Delphi thread or an external.
For example one of the 'unidentified' - external - threads I did not create has following call stack:
While a Delphi thread I created for testing purposes has following, where the Delphi units are recognizable:
Related
I have an application that has multiple screens and a process that needs to get UI info from some and update others.
Tried many methods but the result always is always "not a Java FX thread". Without using some kind of thread the UI does not update Because of the multi screen nature of the app (not practical to change) I need to fundamentally change the application architecture which is why I am not posting any code - its all going to change.
What I cant work out is the best way to do this and as any changes are likely to require substantial work I am reluctant to try something that has little chance of success.
I know about Platform.runLater and tried adding that to the updates but that was complex and did not seem to be effective.
I do have the code on GitHub - its a personal leaning project that started in Scala 2 but if you have an interest in learning or pointing out my errors I can provide access.
Hope you have enjoyed a wonderful Christmas.
PS just make the repo public https://github.com/udsl/Processor6502
The problem is not that the Platform.runLater was not working its because the process is being called form a loop in a thread and without a yield the JavaFX thread never gets an opportunity to run. It just appeared to be failing – again I fall foul of an assumption.
The thread calls a method from within a loop which terminates on a condition set by the method.
The process is planned to emulate the execution of 6502 processor instructions in 2 modes run and run-slow, run-slow is run with a short delay after each instruction execution.
The updates are to the main screen the PC, status flags and register contents. The run (debug) screen gets the current instruction display updated and other items will be added. In the future.
The BRK instruction with a zero-byte following is captures and set the execution mode to single-step essentially being a break point though in the future it will be possible via the debug screen to set a breakpoint and for the execution of the breakpoint to restore the original contents. This is to enable the debugging of a future hardware item – time and finances permitting – it’s a hobby after all 😊
It terns out that the JavaFX thread issue only happens when a FX control is written to but not when read from. Placing all reads and writes in a Platform.runLater was too complex which is why I was originally searching for an alternative solution but now only needed it protect the writes is much less a hassle.
In the process loop calling Thread.’yield’() enables the code in the Platform.runLater blocks to be executed on the JavaFX thread so the UI updates without an exception.
The code in the Run method:
val thread = new Thread {
override def run =
while runMode == RunMode.Running || runMode == RunMode.RunningSlow do
executeIns
Thread.`yield`()
if runMode == RunMode.RunningSlow then
Thread.sleep(50) // slow the loop down a bit
}
thread.start
Note that because yield is a Scala reserved word needs to quote it!
I have a C++ application on Mac OS X. The app runs an event processing with the glfw library on the main thread and reads input and execute commands on a background C++ std::thread.
I am observing a frustrating phenomenon that I cannot explain so far.
If I make a call to a long running function on the background thread, initially that thread is using 100% of a core. But, after it has used a few seconds of CPU (10 seems to be the magic threshold), it gets throttled down to 25%.
If I start a computation run on a thread in the background before starting the glfw event processing loop (the event processing is essentially stuck waiting for events, as I don't even open a window), then it can use 100% for as long as it wants.
My biggest problem is that I have no idea what could be causing this nor how to figure it out. I've tested retrieving the pthread sched_param and changing the sched_priority from what seems to be default 31 to various values between 20 and 60 and it does not help.
I have identified one more condition for the phenomenon to happen:
The background thread has to have read from the terminal. It happens when I run the following background thread and enter a line for the computation to take place:
std::thread cmd([argc, argv, &scriptingRunner] {
for (std::string line; std::getline(std::cin, line); ) {
longComputation();
}
Perhaps App Nap is throttling your application to save energy. To check, open the Activity Monitor program and right-click on the header of the processes table to bring up the context menu, and click on "App Nap" in the context menu to enable the App Nap column; then look at your process in the table and see if its value in the App Nap column switches to "Yes" when the fault occurs.
If you want to disable app nap for your app, see the code listed in the question here.
I know very similar questions have been asked before, but I am unable to find an answer for my specific problem. I have a main (GUI) thread which upon button press initializes a worker thread to perform some analysis. I am using signals and slots to communicate between my worker thread and my GUI thread (i.e. when the thread starts and when it finishes), but I need to go deeper than that. My worker thread actually calls another class in a separate implementation file which then iterates through a series of calculations which are sent to std::cout for each iteration (as the code used to be a console application for which I am now writing a GUI). I am trying to feed those outputs for each iteration back into my GUI thread so that my text browser is updated in real time as my code iterates. The problem is, when I emit a signal from the class my worker thread calls, it is not picked up by the GUI thread. I do not get any errors. Does anyone have any suggestions on how to transmit a signal to the GUI from a class that my worker thread is calling? I can post code as required, but I'm not sure what would be most helpful to see and my code is quite extensive (it's an aircraft performance application). Any help would be greatly appreciated. Thank you kindly!
1) Make sure the connect() call for connecting you signal returns true. If it does not, qdebug output usually tells you what is wrong
2) You should use the QueuedConnection type (the default (Auto) should work also)
I have a worker thread in a class that is owned by a ChildView. (I intend to move this to the Doc eventually.) When the worker thread completes a task I want all the views to be updated. How can I make a call to tell the Doc to issue an UpdateAllViews()? Or is there a better approach?
Thank you.
Added by OP: I am looking for a simple solution. The App is running on a single user, single CPU computer and does not need network (or Internet) access. There is nothing to cause a deadlock.
I think I would like to have the worker thread post (or send) a message to cause the views to update.
Everything I read about threading seems way more complicated than what I need - and, yes, I understand that all those precautions are necessary for applications that are running in multiprocessor, multiuser, client-server systems, etc. But none of those apply in my situation.
I am just stuck at getting the right combination of getting the window handle, posting the message and responding to the message in the right functions and classes to compile and function at all.
UpdateAllViews is not thread-safe, so you need to marshal the call to the main thread.
I suggest you to signal a manual-reset event to mark your thread's completion and check the event's status in a WM_TIMER handler.
suggested reading:
First Aid for the Thread-Impaired:
Using Multiple Threads with MFC
More First Aid for the Thread
Impaired: Cool Ways to Take Advantage
of Multithreading
my question is : how can I use SendMessage() to implement thread communication between two threads, one with a window (GUI) and the other with no window?
The problem is that SendMessage() needs a handle (HWND)?
Another detail about my project : Two threads, one running managed code (the one with the user interface), and the other running native code (the one without window)
Thank you very much!
I would suggest creating a hidden window. When using postthreadmessage, there is a chance that your message could get lost (ie: if a messagebox is running the message loop).
More info about that at:
http://blogs.msdn.com/oldnewthing/archive/2005/04/26/412116.aspx
Perhaps you should try to use PostMessage or PostThreadMessage
If the thread has no window, no message queue, and no message dispatcher, then it's going to be hard to a message to it. It is common for threads to create hidden windows just for communication purposes (take a look with Windows Spy and you'll see plenty of examples).
One alternative is to use shared memory and a synchronization primitive such an event or semaphore. Another alternative is to use pipes.
what #jdigital said. Note that if you create a hidden window, and your thread does not already implement a message loop (either in regular win32-speak, or one in the context of a COM STA -- and if you have no idea what I'm talking about then one probably does not exist in your thread), you'll also want to create a message loop as well. ATL makes it fairly easy with _AtlModule.RunMessageLoop(); Unfortunately this also means the thread in question is probably going to need to be event-driven while it is in the message loop. You can do tricky things like MsgWaitForMultipleObjects, but it gets hairy.
Here's an example of hidden windows if you're familiar with ATL/COM. I went through this pain a while back and thought there was a useful discussion on microsoft.public.vc.atl, but the best I can find now is this post. which goes into some detail about variants of message loops (what to do differently if you have keystroke accelerators or modeless windows, sounds like you don't in your application).