Hi
I have following problem: I'm creating two threads who are performing some
tasks. When one thread finished I would like to restart her again (e.g. new
job). Following example demonstrates that. Problem is that when program is
started many threads are created (see output section), when only two should
be running at any time. Can you please help me to identify me where the
problem is?
Best regards
Ivan
Source
=============== =
private void btnStartThreads _Click(object sender, System.EventArg s e)
{
JobAgent ag1 = new JobAgent ();
JobAgent ag2 = new JobAgent ();
while (true)
{
if (ag1.IsRunning == false)
{
Thread t1 = new Thread (new ThreadStart (ag1.Run));
t1.Start ();
}
if (ag2.IsRunning == false)
{
Thread t2 = new Thread (new ThreadStart (ag2.Run));
t2.Start ();
}
}
}
}
public class JobAgent
{
protected ThreadStatus status = new ThreadStatus ();
public void Run ()
{
IsRunning = true;
Debug.WriteLine ("Thread num. " + Convert.ToStrin g
(Thread.Current Thread.GetHashC ode ()) + " started");
Thread.Sleep (5000);
Debug.WriteLine ("Thread num. " + Convert.ToStrin g
(Thread.Current Thread.GetHashC ode ()) + " finished");
IsRunning = false;
}
public bool IsRunning
{
get
{
lock (status)
{
return status.isRunnin g;
}
}
set
{
lock (status)
{
status.isRunnin g = value;
}
}
}
}
public class ThreadStatus
{
public bool isRunning = false;
}
}
Output
=============== =
Thread num. 10 started
Thread num. 13 started
Thread num. 14 started
Thread num. 15 started
Thread num. 16 started
Thread num. 17 started
Thread num. 18 started
Thread num. 58 started
Thread num. 11 started
Thread num. 12 started
Thread num. 19 started
Thread num. 20 started
Thread num. 21 started
Thread num. 22 started
Thread num. 23 started
Thread num. 24 started
Thread num. 57 started
Thread num. 25 started
Thread num. 26 started
Thread num. 27 started
Thread num. 28 started
Thread num. 10 finished
The thread '<No Name>' (0x1544) has exited with code 0 (0x0).
Thread num. 13 finished
The thread '<No Name>' (0x12dc) has exited with code 0 (0x0).
Thread num. 14 finished
The thread '<No Name>' (0xabc) has exited with code 0 (0x0).
Thread num. 15 finished
The thread '<No Name>' (0x930) has exited with code 0 (0x0).
Thread num. 17 finished
Thread num. 18 finished
The thread '<No Name>' (0xd7c) has exited with code 0 (0x0).
Thread num. 16 finished
The thread '<No Name>' (0xda8) has exited with code 0 (0x0).
Thread num. 29 started
The thread '<No Name>' (0x1590) has exited with code 0 (0x0).
7  2703 
Ivan <no******@today .com> wrote: I have following problem: I'm creating two threads who are performing some
tasks. When one thread finished I would like to restart her again (e.g. new
job). Following example demonstrates that. Problem is that when program is
started many threads are created (see output section), when only two should
be running at any time. Can you please help me to identify me where the
problem is?
Well for one thing, there's nothing to say that just because you've
called Start on the thread, the first line of the method you've
specified will have run.
I would suggest using events and the like to signal when a job has
finished, rather than relying on a status flag like this.
--
Jon Skeet - <sk***@pobox.co m> http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
I thought about events, but how can I achieve that only one thread per time
can fire that event (if two threads end at same time and try to fire e.g.
ThreadFinished event at the same time)?
Ivan
"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** @msnews.microso ft.com... Ivan <no******@today .com> wrote: I have following problem: I'm creating two threads who are performing
some tasks. When one thread finished I would like to restart her again (e.g.
new job). Following example demonstrates that. Problem is that when program
is started many threads are created (see output section), when only two
should be running at any time. Can you please help me to identify me where the
problem is?
Well for one thing, there's nothing to say that just because you've
called Start on the thread, the first line of the method you've
specified will have run.
I would suggest using events and the like to signal when a job has
finished, rather than relying on a status flag like this.
--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Ivan <no******@today .com> wrote: I thought about events, but how can I achieve that only one thread per time
can fire that event (if two threads end at same time and try to fire e.g.
ThreadFinished event at the same time)?
Well, you can use locking to make sure that only one of the threads is
executing the event handler at any one time...
--
Jon Skeet - <sk***@pobox.co m> http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Hi Ivan,
Even without events your code is ok. The problem is the moment you set the
IsRunning flag.
You cannot guarantee that the loop in the main thread wont run several times
before the first line of the worker thread set the falg. And you will endup
with many threads started. That's what actually happens.
to make your code work set the falg right before starting the thread
The loop should look like this
while (true)
{
if (ag1.IsRunning == false)
{
Thread t1 = new Thread (new ThreadStart (ag1.Run));
ag1.IsRunning = true;
t1.Start ();
}
if (ag2.IsRunning == false)
{
Thread t2 = new Thread (new ThreadStart (ag2.Run));
ag2.IsRunning = true;
t2.Start ();
}
}
remove setting the flag to true at the beginning of the Run method. Leave
setting the flag to false, though.
Run method should look like this.
public void Run ()
{
Console.WriteLi ne ("Thread num. " + Convert.ToStrin g
(Thread.Current Thread.GetHashC ode ()) + " started");
Thread.Sleep (5000);
Console.WriteLi ne ("Thread num. " + Convert.ToStrin g
(Thread.Current Thread.GetHashC ode ()) + " finished");
IsRunning = false;
}
Now ot will work correctly. However the main thread doesn't need to know
anything about setting that flag, as a matter of fact it doesn't need to
know that there are threads at all. So, my suggestion is to move the code
for starting the thread and setting the flag in the JobAgen class. The main
thread in this case will look as follows
while (true)
{
if (!ag1.IsBusy)
{
ag1.DoJob()
}
if (!ag2.IsBusy)
{
ag2.DoJob();
}
}
--
HTH
Stoitcho Goutsev (100) [C# MVP]
"Ivan" <no******@today .com> wrote in message
news:cc******** **@fegnews.vip. hr... I thought about events, but how can I achieve that only one thread per
time can fire that event (if two threads end at same time and try to fire e.g.
ThreadFinished event at the same time)?
Ivan
"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** @msnews.microso ft.com... Ivan <no******@today .com> wrote: I have following problem: I'm creating two threads who are performing some tasks. When one thread finished I would like to restart her again
(e.g. new job). Following example demonstrates that. Problem is that when
program is started many threads are created (see output section), when only two should be running at any time. Can you please help me to identify me where
the problem is?
Well for one thing, there's nothing to say that just because you've
called Start on the thread, the first line of the method you've
specified will have run.
I would suggest using events and the like to signal when a job has
finished, rather than relying on a status flag like this.
--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Thx. for help. I think that there is similar problem when thread ends: it
sets the flag that is not busy (last statement in thread), but thread will
be actualy terminated few milliseconds after. Is there some better way to
achieve same functionality like in example and to get complete
synchronization ?
Ivan
"Stoitcho Goutsev (100) [C# MVP]" <10*@100.com> wrote in message
news:uF******** ******@TK2MSFTN GP10.phx.gbl... Hi Ivan,
Even without events your code is ok. The problem is the moment you set the
IsRunning flag.
You cannot guarantee that the loop in the main thread wont run several
times before the first line of the worker thread set the falg. And you will
endup with many threads started. That's what actually happens.
to make your code work set the falg right before starting the thread
The loop should look like this
while (true)
{
if (ag1.IsRunning == false)
{
Thread t1 = new Thread (new ThreadStart (ag1.Run));
ag1.IsRunning = true;
t1.Start ();
}
if (ag2.IsRunning == false)
{
Thread t2 = new Thread (new ThreadStart (ag2.Run));
ag2.IsRunning = true;
t2.Start ();
}
}
remove setting the flag to true at the beginning of the Run method. Leave
setting the flag to false, though.
Run method should look like this.
public void Run ()
{
Console.WriteLi ne ("Thread num. " + Convert.ToStrin g
(Thread.Current Thread.GetHashC ode ()) + " started");
Thread.Sleep (5000);
Console.WriteLi ne ("Thread num. " + Convert.ToStrin g
(Thread.Current Thread.GetHashC ode ()) + " finished");
IsRunning = false;
}
Now ot will work correctly. However the main thread doesn't need to know
anything about setting that flag, as a matter of fact it doesn't need to
know that there are threads at all. So, my suggestion is to move the code
for starting the thread and setting the flag in the JobAgen class. The
main thread in this case will look as follows
while (true)
{
if (!ag1.IsBusy)
{
ag1.DoJob()
}
if (!ag2.IsBusy)
{
ag2.DoJob();
}
}
--
HTH
Stoitcho Goutsev (100) [C# MVP]
"Ivan" <no******@today .com> wrote in message
news:cc******** **@fegnews.vip. hr... I thought about events, but how can I achieve that only one thread per
time can fire that event (if two threads end at same time and try to fire
e.g. ThreadFinished event at the same time)?
Ivan
"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** @msnews.microso ft.com... Ivan <no******@today .com> wrote:
> I have following problem: I'm creating two threads who are
performing some > tasks. When one thread finished I would like to restart her again
(e.g. new > job). Following example demonstrates that. Problem is that when
program is > started many threads are created (see output section), when only two
should > be running at any time. Can you please help me to identify me where
the > problem is?
Well for one thing, there's nothing to say that just because you've
called Start on the thread, the first line of the method you've
specified will have run.
I would suggest using events and the like to signal when a job has
finished, rather than relying on a status flag like this.
--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
> Thx. for help. I think that there is similar problem when thread ends: it sets the flag that is not busy (last statement in thread), but thread will
be actualy terminated few milliseconds after.
I don't see a problem there. The thread will end some time after, but since
it wont do any work you don't have to worry. Anyways next time you'll create
a new one
achieve same functionality like in example and to get complete
synchronization ?
I presonally don't see anything wrong with that one. You shouldn't go too
complex for such simple sync scenario
--
Stoitcho Goutsev (100) [C# MVP]
Thx. your comments are very helpful.
Best regards
Ivan
"Stoitcho Goutsev (100) [C# MVP]" <10*@100.com> wrote in message
news:eD******** ******@TK2MSFTN GP10.phx.gbl... Thx. for help. I think that there is similar problem when thread ends:
it sets the flag that is not busy (last statement in thread), but thread
will be actualy terminated few milliseconds after.
I don't see a problem there. The thread will end some time after, but
since it wont do any work you don't have to worry. Anyways next time you'll
create a new one
achieve same functionality like in example and to get complete
synchronization ?
I presonally don't see anything wrong with that one. You shouldn't go too
complex for such simple sync scenario
--
Stoitcho Goutsev (100) [C# MVP]
This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
by: Steven Brown |
last post by:
I'm trying to figure out how to safely use .NET events/delegates in a
thread-safe class. There are a couple problems. One is that the standard
"if(EventName != null) EventName(...);" call can fail if the event is
emptied of all methods between the two statements, implying that some sort
of synchronization between this and removals from EventName is needed. The
other problem is that if an event with a set of delegates is in the process...
|
by: scott |
last post by:
hi all,
Thx to any one that can offer me help, it will be much appreciated.
iv got a multithreaded program and need to use thread synchronization. The
synchronization does not have to work across multiple processes just the
one. I was wondering if any one new which one used the least overhead. Im
at current using mutexes but was wondering if there was something a bit
|
by: Bob Day |
last post by:
Using VS 2003, VB, MSDE...
There are two threads, A & B, that continously run and are started by Sub
Main. They instantiationsl of identical code. Thread A handles call
activity on telephone line 1 and Thread B handles call activity on telephone
line 2. They use a common SQL datasource, but all DataSets are unique to
each thread.
Is there a way for thread A to occasionally communication to thread B that
something has happened? ...
|
by: Robert Speck |
last post by:
Hi there,
Can anyone shed anymore light on why "Thread.Suspend()" has been deprecated
by MSFT beyond what MSDN says about it. I'm not sure if I quite appreciate
the various pitfalls they discuss but using it under certain circumstances
still seems reasonable. For instance, I want to display a small modal dialog
with a "Cancel" button which allows the user to abort a background thread.
If the user clicks this button, I then want to prompt...
|
by: fniles |
last post by:
I create a thread where I pass thru a message. When I click very fast many
times (like 50 times) to create 50 threads, the message did not get pass
thru ProcessMessage.
For example: strBuffer = "#TRADE, D1410-123456, BUY, 1, ESM7, DAY, LIMIT,
1490.00, , , 0, 0, 0, 0, 0, links |52994/25/2007 10:47:17 AM !A", when I
trigger to create many threads (like 50), this message did not get to sub
ProcessMessage in clsEachMessage.
I have added...
| | |
by: arun.darra |
last post by:
Are the following thread safe:
1. Assuming Object is any simple object
Object* fn()
{
Object *p = new Object();
return p;
}
2. is return by value thread safe?
|
by: sundman.anders |
last post by:
Hi all!
I have a question about thread synchronization and c++ streams
(iostreams, stringstreams, etc). When optimizing a program for a
multicore processor I found that stringstream was causing a LOT of
synchronization overhead. After a bit of digging I concluded that this
synchronization has to do with the access to a global locale inside
the stream.
The problem can be seen by running the small distilled benchmark code
|
by: Hapa |
last post by:
Does only reading (never writing) of a variable need thread synchronisation?
Thanks for help?
PS.
Anybody knows a Visual C++ news group?
|
by: Markus |
last post by:
Hello everyone.
Recently I stumbled upon an interesting problem related to thread-parallel
programming in C (and similarily C++). As an example assume a simple "buffer"
array of size 8, e.g. with static lifetime and exteral linkage. One thread fills
the buffer structure, and the other in some way evaluates its contents, e.g.
do {
synchronize_with_other_thread();
for (int i=0;i<8;++i) {
|
by: marktang |
last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look !
Part I. Meaning of...
|
by: jinu1996 |
last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth.
The Art of Business Website Design
Your website is...
| | |
by: Hystou |
last post by:
Overview:
Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For most users, this new feature is actually very convenient. If you want to control the update process,...
|
by: agi2029 |
last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own....
Now, this would greatly impact the work of software developers. The idea...
|
by: isladogs |
last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM).
In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules.
He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms.
Adolph will...
|
by: adsilva |
last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
|
by: 6302768590 |
last post by:
Hai team
i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
|
by: muto222 |
last post by:
How can i add a mobile payment intergratation into php mysql website.
| | |
by: bsmnconsultancy |
last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...
| |
