locking | 易学教程

PThread RWLock Deadlocking with Recursive Locks

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问题 I've been working on a small sand-boxed example to help me figure out how to use rwlocks. Everything seems fairly straightforward, however I'm getting deadlocks in my example every once and a while and don't understand why it's happening. I've put the code example on pastebin because it's more than a few lines of code: http://pastebin.org/359203 If you run the example. When it eventually deadlocks the last three print statements will be one of two cases: one: th4: request lock th3: request

2 questions on locks performance/use

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问题 On the server application, I need to assign to each connected client an unique ID, so I am doing it this way: private short GetFreeID() { lock (this.mUsedPlayerIDsSynchronization) { for (short I = 1; I < 500; I++) { if (ClientIDPool[I] == false) { ClientIDPool[I] = true; return I; } } return -1; } } My first question: Could it be done more efficiently, I mean with better performance? I have read here that we should learn to write code without locks. I have also read there for some atomic

How to make wordpress blog completely invisible to public [Not Private]

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问题 I want to close a wordpress blog I have from the public and keep it only for myself. I know I can set it to private but it shows an uggly log-in page and I dont want people trying to access it (using random usernames/pass etc) or think that its still open but its for members with accounts or anything like that. I would like the blog to point to a " server not found " for the public and when I am logged in as admin to be able to see my posts and backend aswell as frontend. How can I make this

MySQL producer consumer with multiple select threads

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I've to following situation: There is a table containing different "jobs" to process and several worker threads consuming those jobs. As I don't want to delete those jobs once finished, I'll just set a "complete" flag for that record. So in fact I've the following workflow (for each processing thread) Select 1st record which is not complete Process job Set "complete" flag How do I prevent other threads from consuming the same job (as setting it to "complete" will take a while). Also just updating the "complete" flag in the 2nd step will cause some jobs to be processed twice as there might be a

Global variable in ASP.NET

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问题 I wish to stop a thread from entering code while another thread is still executing that bit of code: I'm currently going the following: global.asax.cs private static bool _isProcessingNewIllustrationRequest; public static bool IsProcessingNewIllustrationRequest { get { return _isProcessingNewIllustrationRequest; } set { _isProcessingNewIllustrationRequest = value; } } Then in MVC: public ActionResult CreateNewApplication() { if (!Global.IsProcessingNewIllustrationRequest) { Global

How can I force a Powershell script to wait overwriting a file until another process is finished reading it?

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问题 Imagine that I have a shared folder MyShared: User A, gets the file \MyShared:\Foo.txt after every 30 seconds. And I overwrite \MyShared:\Foo.txt also after every 28 seconds (within my PowerShell script) How can I prevent myself to overwrite this file while the user is getting it, in PowerShell? (I do not want to break the content of the file or end-up with some error by attempting to overwrite it in the time of user retrieving it) If I rephrase the question : How can I force a Powershell

System.ArgumentNullException in ResourceManager.GetString internals

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问题 My code: System.Resources.ResourceManager resourceManager = GetResourceManager(); string str = resourceManager.GetString("delete", new CultureInfo(1033)); In current project compiled under .NET 2.0 everything works as excepted. Variable str contains resource string for LCID 1033 - Delete , this is ok. We are now upgrading to .NET 4.0, recompiled project under target framework .NET 4.0. Now compiled as .NET 4.0 assemblies, it throws exception System.ArgumentNullException with message Value

How to replace a concurrently instance without losing data?

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问题 I have many threads who save the state and one thread that logs the state. I'd like to not lose data, which means to always log the latest state. The solution I have is to use a read-write lock when replacing/clearing the stats collection, which will not loose data but looks very cumbersome. See code below. What I would like is some way to run some code atomically while an instance isn't changed. Needless to say that the instance change should be atomically as well. The cumbersome solution

What are the pros and cons of using closures instead of locks for shared state?

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问题 I'm trying to assess what is the fastest solution for sharing state across a single-writer, single-reader scenario, where the reader just consumes the latest value of a state variable assigned by the writer . The shared state can be of any managed type (i.e. reference or value types). Ideally the synchronization solution would work as fast as the naive non-synchronized solution as possible, since the method will be used for both single-threaded and multi-threaded scenarios potentially

SQLAlchemy session and connection relationship

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问题 Do queries executed with the same SQLAlchemy session object use the same underlying connection? If not, is there a way to ensure this? Some background: I have a need to use MySQL's named lock feature, i.e. GET_LOCK() and RELEASE_LOCK() functions. As far as the MySQL server is concerned, only the connection that obtained the lock can release it - so I have to make sure that I either execute these two commands within the same connection or the connection dies to ensure the lock is released. To