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Home » Community » Newbie corner » Program didn't exit in Task Manager after click [X]
Program didn't exit in Task Manager after click [X] [message #55268] Mon, 26 October 2020 02:36 Go to next message
sinpeople is currently offline  sinpeople
Messages: 29
Registered: October 2020
Location: Singapore
Promising Member

Hi folks,

I have a dialog program which contains a "Start" button to start 2x thread services. It is copied and modified from an existing program. The original program does not have this program but this program has. I tried to isolate the program as the following:
1) Launch program, click [X] directly, program can exit
2) Launch program, click "Start" button, then click [X], program cannot exit.
I could not spot anything suspicious in the callback code of the button handling.
It is the following:

	btnStart <<= callback(this, &RegionalCtrl::SpawnTasks);



void RegionalCtrl::SpawnTasks()
{
	//Start Thread Remote Request; The Server Portion of the UDP TCP Service for Incoming Service
	//Request
	Thread udprpc;
	udprpc.Run(callback(this, &RegionalCtrl::UDPRpcServerThread));
	
	Thread tcprpc;
	tcprpc.Run(callback(this, &RegionalCtrl::TCPRpcServerThread)); 
	
	btnStart.Disable();
}

// Listenning here to figure any execution is needed
void RegionalCtrl::UDPRpcServerThread()
{
	UrrServer urr;
	urr.Create(m_nServerPort); 
	//Cout() << "URR Ping server\n";
	//while(false)
	for(;;) 
	{
		UrrRequest r;
		if(urr.Accept(r)) 
		{
			UdpRpcCmd(r);
		}
		Sleep(500);
	}
}

void RegionalCtrl::TCPRpcServerThread()
{
	TcpSocket server;
	if(!server.Listen(m_nServerPort+100, 5)) {
		Cout() << "Unable to initialize server socket!\n";
		SetExitCode(1);
		return;
	}
	Cout() << "Waiting for requests..\n";
	for(;;) 
	{
		TcpSocket s;
		if(s.Accept(server)) {
			String w = s.GetLine();
			TcpRpcCmd(w);
//			Cout() << "Request: " << w << " from: " << s.GetPeerAddr() << '\n';
			if(w == "time")
				s.Put(AsString(GetSysTime()));
			else
				s.Put(AsString(3 * atoi(~w)));
			s.Put("\n");
		}
		Sleep(500);
	}
}



I stepped into these 2 pieces of code. It didn't return back when the "if" statement is stepped into to get input strings. Comment either one of these 2 threads didn't help, unless comment both of them.

I have to kill the program every time when it is launched outside theIDE. It can exited properly if I launch it within theIDE for debug though. I checked back to the original program. These pieces of code are the same. Headache. Not sure what's the general advise to troubleshoot this kind of "Fail to exit completed from OS" problem.

Thank you very much!

Best Regards
David
Re: Program didn't exit in Task Manager after click [X] [message #55270 is a reply to message #55268] Mon, 26 October 2020 08:47 Go to previous messageGo to next message
mirek is currently offline  mirek
Messages: 14105
Registered: November 2005
Ultimate Member
sinpeople wrote on Mon, 26 October 2020 02:36
Hi folks,

I have a dialog program which contains a "Start" button to start 2x thread services. It is copied and modified from an existing program. The original program does not have this program but this program has. I tried to isolate the program as the following:
1) Launch program, click [X] directly, program can exit
2) Launch program, click "Start" button, then click [X], program cannot exit.
I could not spot anything suspicious in the callback code of the button handling.
It is the following:

	btnStart <<= callback(this, &RegionalCtrl::SpawnTasks);



void RegionalCtrl::SpawnTasks()
{
	//Start Thread Remote Request; The Server Portion of the UDP TCP Service for Incoming Service
	//Request
	Thread udprpc;
	udprpc.Run(callback(this, &RegionalCtrl::UDPRpcServerThread));
	
	Thread tcprpc;
	tcprpc.Run(callback(this, &RegionalCtrl::TCPRpcServerThread)); 
	
	btnStart.Disable();
}

// Listenning here to figure any execution is needed
void RegionalCtrl::UDPRpcServerThread()
{
	UrrServer urr;
	urr.Create(m_nServerPort); 
	//Cout() << "URR Ping server\n";
	//while(false)
	for(;;) 
	{
		UrrRequest r;
		if(urr.Accept(r)) 
		{
			UdpRpcCmd(r);
		}
		Sleep(500);
	}
}

void RegionalCtrl::TCPRpcServerThread()
{
	TcpSocket server;
	if(!server.Listen(m_nServerPort+100, 5)) {
		Cout() << "Unable to initialize server socket!\n";
		SetExitCode(1);
		return;
	}
	Cout() << "Waiting for requests..\n";
	for(;;) 
	{
		TcpSocket s;
		if(s.Accept(server)) {
			String w = s.GetLine();
			TcpRpcCmd(w);
//			Cout() << "Request: " << w << " from: " << s.GetPeerAddr() << '\n';
			if(w == "time")
				s.Put(AsString(GetSysTime()));
			else
				s.Put(AsString(3 * atoi(~w)));
			s.Put("\n");
		}
		Sleep(500);
	}
}



I stepped into these 2 pieces of code. It didn't return back when the "if" statement is stepped into to get input strings. Comment either one of these 2 threads didn't help, unless comment both of them.

I have to kill the program every time when it is launched outside theIDE. It can exited properly if I launch it within theIDE for debug though. I checked back to the original program. These pieces of code are the same. Headache. Not sure what's the general advise to troubleshoot this kind of "Fail to exit completed from OS" problem.

Thank you very much!

Best Regards
David


Would it possible to post the whole package? I do not even know which "if" statement do you have in mind...

Mirek
Re: Program didn't exit in Task Manager after click [X] [message #55271 is a reply to message #55270] Mon, 26 October 2020 10:01 Go to previous messageGo to next message
sinpeople is currently offline  sinpeople
Messages: 29
Registered: October 2020
Location: Singapore
Promising Member

Hi

Thank you for your reply. I have attached the zip package. The .xml configurations are also included.

Extract the zip to MyApp folder to run the RegionalCtrl


Best Regards
David
  • Attachment: MyApps.zip
    (Size: 42.24KB, Downloaded 172 times)

[Updated on: Mon, 26 October 2020 10:16]

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Re: Program didn't exit in Task Manager after click [X] [message #55389 is a reply to message #55271] Thu, 05 November 2020 13:51 Go to previous messageGo to next message
peterh is currently offline  peterh
Messages: 108
Registered: November 2018
Location: Germany
Experienced Member
While in the debugger, the program doesnt stop either.
If I click [x], the window is closed, but the stop button of the debugger stays red and CPU-load in Windows Task manager is high.
In the "threads" section of the debugger it can be seen, several threads are still running and waiting inside windows e.g. "WaitForMultipleObjects".
If the red stop button of the debugger is clicked, the threads are terminated, so the debugger can do this, but the program obviously does not successfully terminate all threads.

Maybe, some threads are blocked on Kernel objects by blocking I/O? In this case these cannot be immediately terminated.
Because the threads can be killed by Windows Task Manager and/or debugger, there is some hope you can kill them programmatically before the main GUI thread terminates.
This is of course a brute force solution, maybe there are better solutions, but I cannot give advice, because I am not specialist for this matter.

Good luck!
P.S. If the programm is running normally it consumes a lot of CPU while doing nothing than waiting.
Maybe this is a side effect of my system configuration or of debugger, I dont know.

[Updated on: Sat, 07 November 2020 08:35]

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Re: Program didn't exit in Task Manager after click [X] [message #55399 is a reply to message #55268] Sat, 07 November 2020 07:53 Go to previous messageGo to next message
peterh is currently offline  peterh
Messages: 108
Registered: November 2018
Location: Germany
Experienced Member
For Windows, this solves the problem, so far I can see:

GUI_APP_MAIN
{
	MainWindow().Sizeable().Run();
	ExitProcess(0);
}


ExitProcess() is a Windows system call that terminates all blocking IO and kills all threads, including main thread and process.
https:// docs.microsoft.com/en-us/windows/win32/procthread/terminatin g-a-process

[Updated on: Sat, 07 November 2020 10:10]

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Re: Program didn't exit in Task Manager after click [X] [message #55401 is a reply to message #55399] Sat, 07 November 2020 11:37 Go to previous messageGo to next message
Klugier is currently offline  Klugier
Messages: 1083
Registered: September 2012
Location: Poland, Kraków
Senior Contributor
Hello Peterh,

The trick with ExitProcess(0) seems like the hack and workaround. In good written application it is never needed. At the end of the program you should clean all resources, threads and processes. If for some reasons you can not close your application then you need to do the investigation and fix your code. Moreover ExitProcess(0) is Windows only and using it you will lose portability.

Klugier


U++ - one framework to rule them all.

[Updated on: Sat, 07 November 2020 11:39]

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Re: Program didn't exit in Task Manager after click [X] [message #55402 is a reply to message #55401] Sat, 07 November 2020 12:01 Go to previous messageGo to next message
peterh is currently offline  peterh
Messages: 108
Registered: November 2018
Location: Germany
Experienced Member
So far I understand it, Windows will not terminate a thread forcefully, but will inject code to the thread, so the thread will terminate itself cleanly, when it runs this code.
This doesnt work, if the thread is IO waiting, because the thread doesnt run. In this case, if there is no IO timeout, the thread cannot self terminate.
So first the IO must be unblocked and ExitProcess does this for all IO in the process and threads. Also DLLS are detached cleanly from the threads.

I think, there is nothing wrong with this. Yes, it is system specific, but multithreading is always somewhat specific to the OS.
For console processes ExitProcess() is called automatically by Windows when Ctrl C is pressed, but not for GUI processes.
This is not a call from the debug API but from normal process API.

A cleaner way would be to set a termination flag which is polled by the threads, and I already tried this with no success.
The threads are blocked in some TCP Network call which obviously has no timeout. Maybe this can be improved, but I dont know.
I dont want to dig so deep into it.

[Updated on: Sat, 07 November 2020 13:17]

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Re: Program didn't exit in Task Manager after click [X] [message #55403 is a reply to message #55402] Sat, 07 November 2020 14:03 Go to previous messageGo to next message
peterh is currently offline  peterh
Messages: 108
Registered: November 2018
Location: Germany
Experienced Member
I have tracked down this by singlestep to some degree:

Core, Socket.cpp
Comments starting "//!!!" are by me.

bool TcpSocket::Accept(TcpSocket& ls)
{
	Close();
	Init();
	Reset();
	ASSERT(ls.IsOpen());
	int et = GetEndTime();
	for(;;) {
		int h = ls.GetTimeout();
		bool b = ls.Timeout(timeout).Wait(WAIT_READ, et);
		ls.Timeout(h); //!!! If I step into this thread is switched, the window appears and I am unable to step further
		if(!b) // timeout
			return false;
		socket = accept(ls.GetSOCKET(), NULL, NULL);
		if(socket != INVALID_SOCKET)   
			break;
		if(!WouldBlock() && GetErrorCode() != SOCKERR(EINTR)) { // In prefork condition, Wait is not enough, as other process can accept
			SetSockError("accept");
			return false;
		}
	}
	mode = ACCEPT;
	return SetupSocket();
}


Im unable to singlestep this somewhere inside this code there happens a threadswitch and the window appears.
This blocks the thread. The problem could be here.
I admit, I dont understand it fully have no clue about Networking code. Embarassed

So far I found, timeout in the socket is set to zero or negative - maybe uninitialized - , this means infinite timeout or blocking, so this is a problem in the user code.
I am not sure about it.

[Updated on: Sat, 07 November 2020 21:06]

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Re: Program didn't exit in Task Manager after click [X] [message #55405 is a reply to message #55403] Sat, 07 November 2020 20:25 Go to previous messageGo to next message
peterh is currently offline  peterh
Messages: 108
Registered: November 2018
Location: Germany
Experienced Member
While debugging I find something suspicious in Core Socket.cpp at line 287 in the constructor of TcpSocket:

TcpSocket::TcpSocket()
{
	ClearError();
	Reset();
	timeout = global_timeout = start_time = Null; //<---- Confusion about NULL and Null?
	waitstep = 10;
	asn1 = false;
}


"Null" is the special "Nuller" of upp and evaluates to 0x8000 0000 here.
If "(int) Null" is propagated to signed 64 bit it gives 0xffff ffff 8000 0000, if "NULL" is propagated it gives 0x0000 0000 0000 0000.
(int) Null / 10000000 will NOT give zero microseconds. There are wrong timeout calculations in this program, and possibly in Upp source.
This is very dangerous, probably you must turn on warnings about unintended implicite int int64 conversions for compilation.
This leads to different behaviour (which I have observed) , when the program is compiled to 32 or 64 bit and I believe there is a bit of confusion about NULL and Null.
However fixing this, improves, but does not fix the current problem.

[Updated on: Sun, 08 November 2020 00:41]

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Re: Program didn't exit in Task Manager after click [X] [message #55406 is a reply to message #55405] Sun, 08 November 2020 13:03 Go to previous messageGo to next message
Oblivion is currently offline  Oblivion
Messages: 1135
Registered: August 2007
Senior Contributor
Hello peterh,

Just to clarify TcpSocket behaviour and its relation to Upp::Null:

Upp::TcpSocket uses a "pseudo-blocking" mechanism.
This means, the platform specific, underlying socket is always in non-blocking mode.
This is by design. From the user's POV, this allow us to use the TcpSocket in blocking, non-blocking, or in a time-constrained mode, easily, depending on our specific use-case.

Enter "Null" value.

Upp::Null, as you've noticed, is a Upp-specific value. It is already defined for int, int64, double and bool types (and can be used wtih other types that define a Nuller). So you should make no assumptions about it.

Null / 100000 can semantically be considered an "undefined behaviour", because we are trying to divide something that doesn't exist.

Hence, timeout = Null, means that there is no timeout.


int   foo1 = Null; // Ok
int64 foo2 = (int) Null; // Not OK! This can be considered a user error.
int64 foo3 = Null; // OK.


Null, assigned to timeout (int), in this context, is used to put the TcpSocket in blocking mode. OTOH, "0" (int) is used to put the TcpSocket into non-blocking mode.
timeout > 0 && timeout <= INT_MAX is a time-constraint (in miliseconds) for a given TcpSocket operation.

Best regards,
Oblivion


[Updated on: Sun, 08 November 2020 13:34]

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Re: Program didn't exit in Task Manager after click [X] [message #55407 is a reply to message #55406] Sun, 08 November 2020 13:39 Go to previous messageGo to next message
peterh is currently offline  peterh
Messages: 108
Registered: November 2018
Location: Germany
Experienced Member
Thank you Oblivion,
Maybe another name instead of "Null" e.g. "Empty" or "Nil" or "Void" would be better.
NULL and Null are easily confused by beginners and due to the polymorphic nature of Null, this semantical error is not captured by the compiler.
This Naming opens all doors for beginner errors. And I think even proffessionals are not immune against these type of error Crying or Very Sad
This happens for example in Urr.cpp
Watchout to the calculations about timeout here:
index.php?t=getfile&id=6275&private=0

Factum is: The timeout in this program doesnt work, the network communication blocks and the program is therefore unable to terminate the threads.
Another factum is: the timeout behaviour changes (but is not correct) when the progam is compiled for a 32 bit target.

I cannot judge were the reason for this is, in Upp or in RegionalCtrl or in both.

[Updated on: Tue, 10 November 2020 10:05]

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Re: Program didn't exit in Task Manager after click [X] [message #55408 is a reply to message #55407] Sun, 08 November 2020 14:32 Go to previous message
Oblivion is currently offline  Oblivion
Messages: 1135
Registered: August 2007
Senior Contributor
Hello peterh,

You are definitely right, it can be confusing sometimes. That is why we have a warning for beginners. Smile

https://www.ultimatepp.org/srcdoc$Core$Caveats_en-us.html

Maybe we should expand the explanation...

About Urr package: I have never used it but indeed there seems to be a problem in Rcv() function.
According to ln: 18, it expects Upp::Null. But on ln 14-15, it does not check the timeout value for Null.
From what I understand, they should be:

time_out.tv_sec = Nvl(timeout, 0) / 1000;
time_out.tv_usec = Nvl(timeout, 0) % 1000 * 1000;


As a side note, I personally wouldn't consider a good practice assigning NULL to anything other than pointers.
(I don't even use NULL fpr pointers anymore as we have nullptr) Smile

Best regards,
Oblivion



[Updated on: Sun, 08 November 2020 15:08]

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