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  • Is ReaderWriterLockSlim.EnterUpgradeableReadLock() essentially the same as Monitor.Enter()?

    - by Neil Barnwell
    So I have a situation where I may have many, many reads and only the occasional write to a resource shared between multiple threads. A long time ago I read about ReaderWriterLock, and have read about ReaderWriterGate which attempts to mitigate the issue where many writes coming in trump reads and hurt performance. However, now I've become aware of ReaderWriterLockSlim... From the docs, I believe that there can only be one thread in "upgradeable mode" at any one time. In a situation where the only access I'm using is EnterUpgradeableReadLock() (which is appropriate for my scenario) then is there much difference to just sticking with lock(){}? Here's the excerpt: A thread that tries to enter upgradeable mode blocks if there is already a thread in upgradeable mode, if there are threads waiting to enter write mode, or if there is a single thread in write mode. Or, does the recursion policy make any difference to this?

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  • Threading calls to web service in a web service - (.net 2.0)

    - by Ryan Ternier
    Got a question regarding best practices for doing parallel web service calls, in a web service. Our portal will get a message, split that message into 2 messages, and then do 2 calls to our broker. These need to be on separate threads to lower the timeout. One solution is to do something similar to (pseudo code): XmlNode DNode = GetaGetDemoNodeSomehow(); XmlNode ENode = GetAGetElNodeSomehow(); XmlNode elResponse; XmlNode demResponse; Thread dThread = new Thread(delegate { //Web Service Call GetDemographics d = new GetDemographics(); demResponse = d.HIALRequest(DNode); }); Thread eThread = new Thread(delegate { //Web Service Call GetEligibility ge = new GetEligibility(); elResponse = ge.HIALRequest(ENode); }); dThread.Start(); eThread.Start(); dThread.Join(); eThread.Join(); //combine the resulting XML and return it. //Maybe throw a bit of logging in to make architecture happy Another option we thought of is to create a worker class, and pass it the service information and have it execute. This would allow us to have a bit more control over what is going on, but could add additional overhead. Another option brought up would be 2 asynchronous calls and manage the returns through a loop. When the calls are completed (success or error) the loop picks it up and ends. The portal service will be called about 50,000 times a day. I don't want to gold plate this sucker. I'm looking for something light weight. The services that are being called on the broker do have time out limits set, and are already heavily logged and audited, so I'm not worried on that part. This is .NET 2.0 , and as much as I would love to upgrade I can't right now. So please leave all the goodies of 2.0 out please.

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  • C#, Can I check on a lock without trying to acquire it?

    - by Biff MaGriff
    Hello, I have a lock in my c# web app that prevents users from running the update script once it has started. I was thinking I would put a notification in my master page to let the user know that the data isn't all there yet. Currently I do my locking like so. protected void butRefreshData_Click(object sender, EventArgs e) { Thread t = new Thread(new ParameterizedThreadStart(UpdateDatabase)); t.Start(this); //sleep for a bit to ensure that javascript has a chance to get rendered Thread.Sleep(100); } public static void UpdateDatabase(object con) { if (Monitor.TryEnter(myLock)) { Updater.RepopulateDatabase(); Monitor.Exit(myLock); } else { Common.RegisterStartupScript(con, AlreadyLockedJavaScript); } } And I do not want to do if(Monitor.TryEnter(myLock)) Monitor.Exit(myLock); else //show processing labal As I imagine there is a slight possibility that it might display the notification when it isn't actually running. Is there an alternative I can use? Edit: Hi Everyone, thanks a lot for your suggestions! Unfortunately I couldn't quite get them to work... However I combined the ideas on 2 answers and came up with my own solution.

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  • Polling servers at the same port - Threads and Java

    - by John
    Hi there. I'm currently busy working on an IP ban tool for the early versions of Call of Duty 1. (Apparently such a feature wasn't implemented in these versions). I've finished a single threaded application but it won't perform well enough for multiple servers, which is why I am trying to implement threading. Right now, each server has its own thread. I have a Networking class, which has a method; "GetStatus" -- this method is synchronized. This method uses a DatagramSocket to communicate with the server. Since this method is static and synchronized, I shouldn't get in trouble and receive a whole bunch of "Address already in use" exceptions. However, I have a second method named "SendMessage". This method is supposed to send a message to the server. How can I make sure "SendMessage" cannot be invoked when there's already a thread running in "GetStatus", and the other way around? If I make both synchronized, I will still get in trouble if Thread A is opening a socket on Port 99999 and invoking "SendMessage" while Thread B is opening a socket on the same port and invoking "GetStatus"? (Game servers are usually hosted on the same ports) I guess what I am really after is a way to make an entire class synchronized, so that only one method can be invoked and run at a time by a single thread. Hope that what I am trying to accomplish/avoid is made clear in this text. Any help is greatly appreciated.

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  • Log RuntimeException thrown from thread created by Spring via the @Async annotation

    - by Eugen
    I'm having some difficulty logging RuntimeException from a thread. My system is: Java 7 (b118), Spring 3.0.5. The threads are not created by hand, but via Spring's @Async annotation, which creates it's own executor behind the scenes, so I don't really have the option of overriding any methods of the thread, FutureTask or anything low level. So my question is if Spring has any support or if there are any best practices for handling (logging) these type of exceptions? Any suggestions are appreciated. Thanks.

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  • iPhone: One Object, One Thread

    - by GingerBreadMane
    On the iPhone, I would like to do some operations on an image in a separate thread. Rather than dealing with semiphores, locking, etc., I'd like to use the 'One Object, One Thread' method of safely writing this concurrent operation. I'm not sure what is the correct way to copy my object into a new thread so that the object is not accessed in the main thread. Do I use the 'copy' method? If so, do I do this before the thread or inside the thread? ... -(void)someMethod{ UIImage *myImage; [NSThread detachNewThreadSelector:@selector(getRotatedImage:) toTarget:self withObject:myImage]; } -(void)getRotatedImage:(UIImage *)image{ ... ... UIImage *copiedImage = [image copy]; ... ... }

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  • pthread_exit and/or pthread_join causing Abort and SegFaults.

    - by MJewkes
    The following code is a simple thread game, that switches between threads causing the timer to decrease. It works fine for 3 threads, causes and Abort(core dumped) for 4 threads, and causes a seg fault for 5 or more threads. Anyone have any idea why this might be happening? #include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <errno.h> #include <assert.h> int volatile num_of_threads; int volatile time_per_round; int volatile time_left; int volatile turn_id; int volatile thread_running; int volatile can_check; void * player (void * id_in){ int id= (int)id_in; while(1){ if(can_check){ if (time_left<=0){ break; } can_check=0; if(thread_running){ if(turn_id==id-1){ turn_id=random()%num_of_threads; time_left--; } } can_check=1; } } pthread_exit(NULL); } int main(int argc, char *args[]){ int i; int buffer; pthread_t * threads =(pthread_t *)malloc(num_of_threads*sizeof(pthread_t)); thread_running=0; num_of_threads=atoi(args[1]); can_check=0; time_per_round = atoi(args[2]); time_left=time_per_round; srandom(time(NULL)); //Create Threads for (i=0;i<num_of_threads;i++){ do{ buffer=pthread_create(&threads[i],NULL,player,(void *)(i+1)); }while(buffer == EAGAIN); } can_check=1; time_left=time_per_round; turn_id=random()%num_of_threads; thread_running=1; for (i=0;i<num_of_threads;i++){ assert(!pthread_join(threads[i], NULL)); } return 0; }

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  • Java - Call to start method on thread : how does it route to Runnable interface's run () ?

    - by Bhaskar
    Ok , I know the two standard ways to create a new thread and run it in Java : 1 Implement Runnable in a class , define run method ,and pass an instance of the class to a new Thread. When the start method on the thread instance is called , the run method of the class instance will be invoked. 2 Let the class derive from Thread, so it can to override the method run() and then when a new instance's start method is called , the call is routed to overridden method. In both methods , basically a new Thread object is created and its start method invoked. However , while in the second method , the mechanism of the call being routed to the user defined run() method is very clear ,( its a simple runtime polymorphism in play ), I dont understand how the call to start method on the Thread object gets routed to run() method of the class implementing Runnable interface. Does the Thread class have an private field of Type Runnable which it checks first , and if it is set then invokes the run method if it set to an object ? that would be a strange mechanism IMO. How does the call to start() on a thread get routed to the run method of the Runnable interface implemented by the class whose object is passed as a parameter when contructing the thread ?

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  • Returning from method inside a @synchronized block

    - by Michael Waterfall
    I'd just like to know if it's advised to return from a method within a @synchronized block? For example: - (id)test { @synchronized(self) { if (a) return @"A"; else return @"B"; } } As opposed to: - (id)test { NSString *value; @synchronized(self) { if (a) value = @"A"; else value = @"B"; } return value; } This sample is rather simplistic, but sometimes in a complex method it would make things simpler to be able to return from within a @synchronized block.

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  • Unresponsive UI when using BeginInvoke

    - by Kazoom
    Bckground I have a networked application written in C#. my server program has a UI and several communication threads, that read from tcp sockets and display messages on controller UI. Communication with each client is done through a seprate thread. When i recieve some stream of messages from one client , the thread for that client writes on UI, which is a richtextbox on a Form. I call SetTextHelper(string text) method of the form. which looks like this private delegate void MyTextUpdateHandler(string text); public void SetTextHelper(string text) { BeginInvoke(new MyTextUpdateHandler(SetText), new object[] { text }); } public setText(string text) { richtext.Text= text; } Question - If i use BeginInvoke my UI is entirely unresponsive when i m writing large stream of data to UI - Invoke solves that problem, but i read that for multi threaded environment where many thereads are sharing same resource Invoke can lead to deadlocks I share the common ichtextbox between around 16 threads - What would be a good desing for my situation?

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  • Thread locking issue with FileHelpers between calling engine.ReadNext() method and readign engine.Li

    - by Rad
    I use producer/consumer pattern with FileHelpers library to import data from one file (which can be huge) using multiple threads. Each thread is supposed to import a chunk of that file and I would like to use LineNumber property of the FileHelperAsyncEngine instance that is reading the file as primary key for imported rows. FileHelperAsyncEngine internally has an IEnumerator IEnumerable.GetEnumerator(); which is iterated over using engine.ReadNext() method. That internally sets LineNumber property (which seems is not thread safe). Consumers will have Producers assiciated with them that will supply DataTables to Consumers which will consume them via SqlBulkLoad class which will use IDataReader implementation which will iterate over a collection of DataTables which are internal to a Consumer instance. Each instance of will have one SqlBulkCopy instance associate with it. I have thread locking issue. Below is how I create multiple Producer threads. I start each thread afterwords. Produce method on a producer instance will be called determining which chunk of input file will be processed. It seems that engine.LineNumber is not thread safe and I doesn't import a proper LineNumber in the database. It seems that by the time engine.LineNumber is read some other thread called engine.ReadNext() and changed engine.LineNumber property. I don't want to lock the loop that is supposed to process a chunk of input file because I loose parallelism. How to reorganize the code to solve this threading issue? Thanks Rad for (int i = 0; i < numberOfProducerThreads; i++) DataConsumer consumer = dataConsumers[i]; //create a new producer DataProducer producer = new DataProducer(); //consumer has already being created consumer.Subscribe(producer); FileHelperAsyncEngine orderDetailEngine = new FileHelperAsyncEngine(recordType); orderDetailEngine.Options.RecordCondition.Condition = RecordCondition.ExcludeIfBegins; orderDetailEngine.Options.RecordCondition.Selector = STR_ORDR; int skipLines = i * numberOfBufferTablesToProcess * DataBuffer.MaxBufferRowCount; Thread newThread = new Thread(() => { producer.Produce(consumer, inputFilePath, lineNumberFieldName, dict, orderDetailEngine, skipLines, numberOfBufferTablesToProcess); consumer.SetEndOfData(producer); }); producerThreads.Add(newThread); thread.Start();} public void Produce(DataConsumer consumer, string inputFilePath, string lineNumberFieldName, Dictionary<string, object> dict, FileHelperAsyncEngine engine, int skipLines, int numberOfBufferTablesToProcess) { lock (this) { engine.Options.IgnoreFirstLines = skipLines; engine.BeginReadFile(inputFilePath); } int rowCount = 1; DataTable buffer = consumer.BufferDataTable; while (engine.ReadNext() != null) { lock (this) { dict[lineNumberFieldName] = engine.LineNumber; buffer.Rows.Add(ObjectFieldsDataRowMapper.MapObjectFieldsToDataRow(engine.LastRecord, dict, buffer)); if (rowCount % DataBuffer.MaxBufferRowCount == 0) { consumer.AddBufferDataTable(buffer); buffer = consumer.BufferDataTable; } if (rowCount % (numberOfBufferTablesToProcess * DataBuffer.MaxBufferRowCount) == 0) { break; } rowCount++; } } if (buffer.Rows.Count > 0) { consumer.AddBufferDataTable(buffer); } engine.Close(); }

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  • Java: How to test methods that call System.exit()?

    - by Chris Conway
    I've got a few methods that should call System.exit() on certain inputs. Unfortunately, testing these cases causes JUnit to terminate! Putting the method calls in a new Thread doesn't seem to help, since System.exit() terminates the JVM, not just the current thread. Are there any common patterns for dealing with this? For example, can I subsitute a stub for System.exit()? [EDIT] The class in question is actually a command-line tool which I'm attempting to test inside JUnit. Maybe JUnit is simply not the right tool for the job? Suggestions for complementary regression testing tools are welcome (preferably something that integrates well with JUnit and EclEmma).

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  • Pass a Message From Thread to Update UI

    - by Jay Dee
    Ive created a new thread for a file browser. The thread reads the contents of a directory. What I want to do is update the UI thread to draw a graphical representation of the files and folders. I know I can't update the UI from within a new thread so what I want to do is: whilst the file scanning thread iterates through a directories files and folders pass a file path string back to the UI thread. The handler in the UI thread then draws the graphical representation of the file passed back. public class New_Project extends Activity implements Runnable { private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { Log.d("New Thread","Proccess Complete."); Intent intent = new Intent(); setResult(RESULT_OK, intent); finish(); } }; public void getFiles(){ //if (!XMLEFunctions.canReadExternal(this)) return; pd = ProgressDialog.show(this, "Reading Directory.", "Please Wait...", true, false); Log.d("New Thread","Called"); Thread thread = new Thread(this); thread.start(); } public void run() { Log.d("New Thread","Reading Files"); getFiles(); handler.sendEmptyMessage(0); } public void getFiles() { for (int i=0;i<=allFiles.length-1;i++){ //I WANT TO PASS THE FILE PATH BACK TU A HANDLER IN THE UI //SO IT CAN BE DRAWN. **passFilePathBackToBeDrawn(allFiles[i].toString());** } } }

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  • using qsub (sge) with multi-threaded applications

    - by dan12345
    i wanted to submit a multi-threaded job to the cluster network i'm working with - but the man page about qsub is not clear how this is done - By default i guess it just sends it as a normal job regardless of the multi-threading - but this might cause problems, i.e. sending many multi-threaded jobs to the same computer, slowing things down. Does anyone know how to accomplish this? thanks. The batch server system is sge.

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  • Is memory allocation in linux non-blocking?

    - by Mark
    I am curious to know if the allocating memory using a default new operator is a non-blocking operation. e.g. struct Node { int a,b; }; ... Node foo = new Node(); If multiple threads tried to create a new Node and if one of them was suspended by the OS in the middle of allocation, would it block other threads from making progress? The reason why I ask is because I had a concurrent data structure that created new nodes. I then modified the algorithm to recycle the nodes. The throughput performance of the two algorithms was virtually identical on a 24 core machine. However, I then created an interference program that ran on all the system cores in order to create as much OS pre-emption as possible. The throughput performance of the algorithm that created new nodes decreased by a factor of 5 relative the the algorithm that recycled nodes. I'm curious to know why this would occur. Thanks. *Edit : pointing me to the code for the c++ memory allocator for linux would be helpful as well. I tried looking before posting this question, but had trouble finding it.

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  • What's Wrong With My VB.NET Code Of Windows Forms Application?

    - by Krishanu Dey
    I've to forms frmPrint & frmEmail and a dataset(MyDataset) with some DataTable and DataTable Adapters. In frmPrint I've the following Sub Public Sub StartPrinting() try adapterLettersInSchedules.Fill(ds.LettersInSchedules) adapterLetters.Fill(ds.Letters) adapterClients.Fill(ds.Clients) adapterPrintJobs.GetPrintJobsDueToday(ds.PrintJobs, False, DateTime.Today) For Each prow As MyDataSet.PrintJobsRow In ds.PrintJobs Dim lisrow As MyDataSet.LettersInSchedulesRow = ds.LettersInSchedules.FindByID(prow.LetterInScheduleID) If lisrow.Isemail = False Then Dim clientrow As MyDataSet.ClientsRow = ds.Clients.FindByClientID(prow.ClientID) Dim letterrow As MyDataSet.LettersRow = ds.Letters.FindByID(lisrow.LetterID) 'prow. 'lisrow.is Label1.SuspendLayout() Label1.Refresh() Label1.Text = "Printing letter" txt.Rtf = letterrow.LetterContents txt.Rtf = txt.Rtf.Replace("<%Firstname%>", clientrow.FirstName) txt.Rtf = txt.Rtf.Replace("<%Lastname%>", clientrow.LastName) txt.Rtf = txt.Rtf.Replace("<%Title%>", clientrow.Title) txt.Rtf = txt.Rtf.Replace("<%Street%>", clientrow.Street) txt.Rtf = txt.Rtf.Replace("<%City%>", clientrow.City) txt.Rtf = txt.Rtf.Replace("<%State%>", clientrow.State) txt.Rtf = txt.Rtf.Replace("<%Zip%>", clientrow.Zip) txt.Rtf = txt.Rtf.Replace("<%PhoneH%>", clientrow.PhoneH) txt.Rtf = txt.Rtf.Replace("<%PhoneW%>", clientrow.PhoneW) txt.Rtf = txt.Rtf.Replace("<%Date%>", DateTime.Today.ToShortDateString) Try PDoc.PrinterSettings = printDlg.PrinterSettings PDoc.Print() prow.Printed = True adapterPrintJobs.Update(prow) Catch ex As Exception End Try End If Next prow ds.PrintJobs.Clear() Catch ex As Exception MessageBox.Show(ex.Message, "Print", MessageBoxButtons.OK, MessageBoxIcon.Error) End Try End Sub And in frmEmail i've the Following Sub Public Sub SendEmails() try adapterLettersInSchedules.Fill(ds.LettersInSchedules) adapterLetters.Fill(ds.Letters) adapterClients.Fill(ds.Clients) adapterEmailJobs.GetEmailJobsDueToday(ds.EmailJobs, False, Today) Dim ls_string As String For Each prow As MyDataSet.EmailJobsRow In ds.EmailJobs Dim lisrow As MyDataSet.LettersInSchedulesRow = ds.LettersInSchedules.FindByID(prow.LetterInScheduleID) If lisrow.Isemail = True Then Dim clientrow As MyDataSet.ClientsRow = ds.Clients.FindByClientID(prow.ClientID) Dim letterrow As MyDataSet.LettersRow = ds.Letters.FindByID(lisrow.LetterID) txt.Rtf = letterrow.LetterContents ls_string = RTF2HTML(txt.Rtf) ls_string = Mid(ls_string, 1, Len(ls_string) - 176) If ls_string = "" Then Throw New Exception("Rtf To HTML Conversion Failed") Label1.SuspendLayout() Label1.Refresh() Label1.Text = "Sending Email" If SendEmail(clientrow.Email, ls_string, letterrow.EmailSubject) Then Try prow.Emailed = True adapterEmailJobs.Update(prow) Catch ex As Exception End Try Else prow.Emailed = False adapterEmailJobs.Update(prow) End If End If Next prow Catch ex As Exception MessageBox.Show(ex.Message, "Email", MessageBoxButtons.OK, MessageBoxIcon.Error) End Try End Sub I'm running this two subs using two different Threads. Public th As New Thread(New ThreadStart(AddressOf StartFirstPrint)) Public th4 As New Thread(New ThreadStart(AddressOf sendFirstEmail)) Here is the code of StartFirstPrint and sendFirstEmail Public Sub StartFirstPrint() Do While thCont Try Dim frm As New frmPrint() 'frm.MdiParent = Me frm.StartPrinting() Catch ex As Exception End Try Loop End Sub Public Sub sendFirstEmail() Do While thCont Try Dim frmSNDEmail As New frmEmail frmSNDEmail.SendEmails() Catch ex As Exception End Try Loop End Sub the thCont is a public boolean variable that specifies when to shop those threads. Most Of the time this works very well. But some times it gives errors Like the following image I don't know why is this occurring. Please help me.

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  • Proper way to have an endless worker thread?

    - by Neil N
    I have an object that requires a lot of initialization (1-2 seconds on a beefy machine). Though once it is initialized it only takes about 20 miliseconds to do a typical "job" In order to prevent it from being re-initialized every time an app wants to use it (which could be 50 times a second or not at all for minutes in typical usage), I decided to give it a job que, and have it run on its own thread, checking to see if there is any work for it in the que. However I'm not entirely sure how to make a thread that runs indefinetly with or without work. Here's what I have so far, any critique is welcomed private void DoWork() { while (true) { if (JobQue.Count > 0) { // do work on JobQue.Pop() } else { System.Threading.Thread.Sleep(50); } } } After thought: I was thinking I may need to kill this thread gracefully insead of letting it run forever, so I think I will add a Job type that tells the thread to end. Any thoughts on how to end a thread like this also appreciated.

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  • How would you implement this "WorkerChain" functionality in .NET?

    - by Dan Tao
    Sorry for the vague question title -- not sure how to encapsulate what I'm asking below succinctly. (If someone with editing privileges can think of a more descriptive title, feel free to change it.) The behavior I need is this. I am envisioning a worker class that accepts a single delegate task in its constructor (for simplicity, I would make it immutable -- no more tasks can be added after instantiation). I'll call this task T. The class should have a simple method, something like GetToWork, that will exhibit this behavior: If the worker is not currently running T, then it will start doing so right now. If the worker is currently running T, then once it is finished, it will start T again immediately. GetToWork can be called any number of times while the worker is running T; the simple rule is that, during any execution of T, if GetToWork was called at least once, T will run again upon completion (and then if GetToWork is called while T is running that time, it will repeat itself again, etc.). Now, this is pretty straightforward with a boolean switch. But this class needs to be thread-safe, by which I mean, steps 1 and 2 above need to comprise atomic operations (at least I think they do). There is an added layer of complexity. I have need of a "worker chain" class that will consist of many of these workers linked together. As soon as the first worker completes, it essentially calls GetToWork on the worker after it; meanwhile, if its own GetToWork has been called, it restarts itself as well. Logically calling GetToWork on the chain is essentially the same as calling GetToWork on the first worker in the chain (I would fully intend that the chain's workers not be publicly accessible). One way to imagine how this hypothetical "worker chain" would behave is by comparing it to a team in a relay race. Suppose there are four runners, W1 through W4, and let the chain be called C. If I call C.StartWork(), what should happen is this: If W1 is at his starting point (i.e., doing nothing), he will start running towards W2. If W1 is already running towards W2 (i.e., executing his task), then once he reaches W2, he will signal to W2 to get started, immediately return to his starting point and, since StartWork has been called, start running towards W2 again. When W1 reaches W2's starting point, he'll immediately return to his own starting point. If W2 is just sitting around, he'll start running immediately towards W3. If W2 is already off running towards W3, then W2 will simply go again once he's reached W3 and returned to his starting point. The above is probably a little convoluted and written out poorly. But hopefully you get the basic idea. Obviously, these workers will be running on their own threads. Also, I guess it's possible this functionality already exists somewhere? If that's the case, definitely let me know!

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  • How do I create a thread-safe write-once read-many value in Java?

    - by Software Monkey
    This is a problem I encounter frequently in working with more complex systems and which I have never figured out a good way to solve. It usually involves variations on the theme of a shared object whose construction and initialization are necessarily two distinct steps. This is generally because of architectural requirements, similar to applets, so answers that suggest I consolidate construction and initialization are not useful. By way of example, let's say I have a class that is structured to fit into an application framework like so: public class MyClass { private /*ideally-final*/ SomeObject someObject; MyClass() { someObject=null; } public void startup() { someObject=new SomeObject(...arguments from environment which are not available until startup is called...); } public void shutdown() { someObject=null; // this is not necessary, I am just expressing the intended scope of someObject explicitly } } I can't make someObject final since it can't be set until startup() is invoked. But I would really like it to reflect it's write-once semantics and be able to directly access it from multiple threads, preferably avoiding synchronization. The idea being to express and enforce a degree of finalness, I conjecture that I could create a generic container, like so: public class WoRmObject<T> { private T object; WoRmObject() { object=null; } public WoRmObject set(T val) { object=val; return this; } public T get() { return object; } } and then in MyClass, above, do: private final WoRmObject<SomeObject> someObject; MyClass() { someObject=new WoRmObject<SomeObject>(); } public void startup() { someObject.set(SomeObject(...arguments from environment which are not available until startup is called...)); } Which raises some questions for me: Is there a better way, or existing Java object (would have to be available in Java 4)? Is this thread-safe provided that no other thread accesses someObject.get() until after it's set() has been called. The other threads will only invoke methods on MyClass between startup() and shutdown() - the framework guarantees this. Given the completely unsynchronized WoRmObject container, it is ever possible under either JMM to see a value of object which is neither null nor a reference to a SomeObject? In other words, does has the JMM always guaranteed that no thread can observe the memory of an object to be whatever values happened to be on the heap when the object was allocated.

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  • .NET threading: how can I capture an abort on an unstarted thread?

    - by Groxx
    I have a chunk of threads I wish to run in order, on an ASP site running .NET 2.0 with Visual Studio 2008 (no idea how much all that matters, but there it is), and they may have aborted-clean-up code which should be run regardless of how far through their task they are. So I make a thread like this: Thread t = new Thread(delegate() { try { /* do things */ System.Diagnostics.Debug.WriteLine("try"); } catch (ThreadAbortException) { /* cleanup */ System.Diagnostics.Debug.WriteLine("catch"); } }); Now, if I wish to abort the set of threads part way through, the cleanup may still be desirable later on down the line. Looking through MSDN implies you can .Abort() a thread that has not started, and then .Start() it, at which point it will receive the exception and perform normally. Or you can .Join() the aborted thread to wait for it to finish aborting. Presumably you can combine them. http://msdn.microsoft.com/en-us/library/ty8d3wta(v=VS.80).aspx To wait until a thread has aborted, you can call the Join method on the thread after calling the Abort method, but there is no guarantee the wait will end. If Abort is called on a thread that has not been started, the thread will abort when Start is called. If Abort is called on a thread that is blocked or is sleeping, the thread is interrupted and then aborted. Now, when I debug and step through this code: t.Abort(); // ThreadState == Unstarted | AbortRequested t.Start(); // throws ThreadStartException: "Thread failed to start." // so I comment it out, and t.Join(); // throws ThreadStateException: "Thread has not been started." At no point do I see any output, nor do any breakpoints on either the try or catch block get reached. Oddly, ThreadStartException is not listed as a possible throw of .Start(), from here: http://msdn.microsoft.com/en-us/library/a9fyxz7d(v=VS.80).aspx (or any other version) I understand this could be avoided by having a start parameter, which states if the thread should jump to cleanup code, and foregoing the Abort call (which is probably what I'll do). And I could .Start() the thread, and then .Abort() it. But as an indeterminate amount of time may pass between .Start and .Abort, I'm considering it unreliable, and the documentation seems to say my original method should work. Am I missing something? Is the documentation wrong? edit: ow. And you can't call .Start(param) on a non-parameterized Thread(Start). Is there a way to find out if a thread is parameterized or not, aside from trial and error? I see a private m_Delegate, but nothing public...

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