Locking allows different types of resources to be locked by a transaction.

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SynchronizedArrayList implemented using reader writer synchronization

I am trying to understand the workings of reader writer locks. For the sake of learning, I implemented reader writer synchronization by my own. I implemented ...
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Portable C++ boost::iterprocess::mutex

I was looking for long time around to have a portable robust solution for multiprocessing synchronization. Who touche this things know that good solution are boost::iterprocess named sync objects. ...
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Lock a process in PHP

We had a situation where it was necessary that a script only be running in one process at a time. The solution was to make a "LockByProcess" class that checks a database for an existing process, and ...
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A simple semaphore in Java

It is a simple semaphore in Java. Although it passes all their tests with flying colors, I'm still not sure it's correct. For example, the last thing I wasn't sure about was ...
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Prevent re-entrant function call in C++

The purpose of this is to prevent a re-entrant function call in a single thread, e.g. prevent the situation where func() calls ...
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0answers
37 views

Moonshot & `Thread.Abort` - dealing with the fallout

Recently, I encountered an anomaly in the manner by which a worker thread was terminated. It prompted me to do some searching and I realized that I was constructing thread code in a haphazard manner. ...
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Social Share count

I am creating a social sharing counter plugin for my WordPress blog. I want to fetch the counts of number of likes, shares, Facebook comments (I am using Facebook comment box), twitter tweet counts ...
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1answer
76 views

Using CountDownLatch for blocking the reads if writes are happening

I am trying to implement lock by which I want to avoid reads from happening whenever I am doing a write on my three maps. Requirements: Reads block until all three maps have been set for the first ...
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1answer
91 views

How to avoid reads before initialization is complete and return updated set of maps value?

This is a follow on to: How to prevent reads before initialization is complete? I am trying to implement lock by which I want to avoid reads from happening whenever I am doing a write on my three ...
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0answers
47 views

Reliability of flock mutex (LOCK_EX|LOCK_NB)

I would like to test reliability of system flock in a multi-threaded and concurrent environment as some suggest that they are not reliable (in comments). Thus I ...
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2answers
166 views

Is this use of a resource based on session ids thread safe?

Let me first describe the expected behavior of the code below: There will be one static SessionManager accessed by many threads. Multiple calls to ...
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3answers
119 views

Feedback on thread safety of the classes

I have following classes. Are they properly guarded for thread safety? Do you see any issues with any of the classes? ...
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1answer
75 views

Operations on files and their locks - code too bulky?

A couple of hours ago I asked a question on Stackoverflow to find out if there is a good way to delete files in a folder only if all files are indeed deletable and I got some good answers that led me ...
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Python app-level document/record locking (eg. for MongoDB)

Introduction MongoDB does not provide means to lock a document (like SELECT FOR UPDATE in RDBMS). There is recommended approach to Isolate Sequence of Operations, which is sometimes called ...
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1answer
146 views

RAII-Style Lockable Objects

TL;DR: Without the phrases "use Boost" and "use C++11", does the posted code for RAII-style locking of a resource look correct and safe, or is there something I've missed. Long Version: I am working ...
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1answer
132 views

C: File locking between server threads

I have written below code where the server is getting requests from clients on socket and creating a thread per client. Each client thread is then writing to a file which is common to all the threads. ...
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1answer
537 views

Locking during cache population

Here I want to lock when populating a particular cache object, without blocking other calls to the same method requesting Foos for other ...
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2answers
218 views

Loading data async with queue. Proper write only locking and scheduling

I have to store and return data on multitasking requests. If data is missing, I schedule loading and return null. I'm using some nubie scheduling by saving current jobs in a list. Also I need data ...
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2answers
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Is this a good way of handling item reservations?

I have a site were we sell unique items. When a user clicks to buy an item we have to reserve it. This prevents other buyers from purchasing the item while the first buyer is checking out. When a ...
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1answer
146 views

Is this the best message delay algorithm?

In my application I am attempting to queue outgoing messages by the following rules By default they should be sent no less than messageDelay apart Some messages ...
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4answers
295 views

Simple multi-threading class: Does anybody spot potential lock-based concurrency issues?

Trying to write a multi-threaded utility that logs some audit trails to the DB every 30 minutes, or whenever my storage data structure (a list in this case) exceeds a certain limit. The code works ...
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Dining philosophers problem

Now I know this dining philosophers problem is researched a lot and there are resources everywhere. But I wrote a simple code to solve this problem with C and then turned to Internet to see if it's ...
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Static class ThreadPool implementation

The following code is a self-implementation of the static class ThreadPool in C#, only the QueueUserWorkItem (the simpler ...
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4answers
3k views

Designing a better logger class

Could you please critisize the logger class below? Can it be used in a multi threaded web environment? If not how can I improve it? Is there anything wrong with locking in WriteToLog method or ...
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3answers
78 views

How to correctly get a IDisposeable when you need to lock the factory?

If I need to create a IDisposeable object from a factory, but if the factory object is not thread safe and requires me to lock on it is this the correct pattern to use? ...
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Getting a decryptor object

I need to lock on my AesManaged instance _Aes to call CreateDecryptor() however the CreateDecryptor() method is not thread safe and this function could be called by ...
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Synced/Atomic access

Forward I would love any comments you have, any ideas, any flaws you can find, and any suggestions you might have regarding the code below. If this is similar to other implementations, I would love ...
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Resource Pool implementation with ReentrantLock and Condition

The Resource Pool is similar to the implementation of a semaphore. It takes the class type of the resource and number of resource pools associated with it as the constructor parameters. There is a ...
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2answers
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Multithreading concepts with Producer Consumer

I just wanted to confirm if this example I created would qualify as a good example of a multithreaded producer consumer. I would like any review changes on improving this example. I found that static ...
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4answers
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Java Non Reentrant Lock Implementation

I have implemented a Non Reentrant Lock. I want to know if this has any mistakes, race conditions etc. I am aware of the fact that existing libraries have to be used (instead of writing our own), but ...
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Concurrency limit map in Go

Please someone who knows locks, mutexes, and Go, review the following code. Task: per host concurrency limits for web crawler (map[string]Semaphore). I considered chan struct{} (chan bool) approach, ...
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Improving handling of data structure used in parallel

I have a class extending the Dictionary class. This class is used for storing some information (modeled in CustomClass) and accessing it through an integer ID. To ...
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768 views

Force locking for thread-safety

After reading Herb Sutter's Associate Mutexes with Data to Prevent Races, I found that my solution was superior in several aspects, least important first: The code is cleaner, without macros No ...
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1answer
437 views

Mutex implementation for uniprocessor bare metal embedded OS

I wrote this recently for one of my projects, any error you guys can spot or a feature which could be implemented without eating up resources or some optimisations ? Oh and it isn't meant for Multi ...
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4answers
239 views

Configurable synchronization approach in Java

I am interested in the community opinion about the following approach for the synchronization. Generally it is based on the idea to have a configurable way to apply locking on some logic parts. Any ...
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2answers
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ReentrantReadWriteLock lock upgrade method

I have a question about lock upgrading.Specifically what bothers me is between readlock.unlock() and following writelock.lock()... I am providing a nearly complete implementation for a sample cache.I ...
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1answer
269 views

std::lock implementation in C with pthreads

I messed a little bit with pthreads and needed an alternative to the C++11 function std::lock (2 args are enough), and this is what I came up with: ...
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1answer
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ReentrantLock with priorities for waiting threads

I am trying to have a ReentrantLock with another way to determinate which thread will have the lock in the waiting queue. ...
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Did I need to use lock to ensure that Queue.Dequeue is Thread Safe in this case on .NET 2.0?

Is this ok? I am using C# and .NET 2.0 I have this Queue declared in my class : ...
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1answer
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Read-write lock implementation for Ruby, new version

I recently discovered that there is no free read-write lock implementation for Ruby available on the Internet, so I built one myself. The intention is to keep it posted on GitHub indefinitely for the ...
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2answers
765 views

Lock-free cache oblivious n-body algorithm

I'm currently looking at, from a rather high level, the parallelization of the gravity calculation in an N-body simulation for approximating a solution to the N-body problem. The simple form of the ...
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1answer
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“Fast” Read/Write Lock

I need a Read-Write lock that is fast and generally portable on Windows machines (including XP, otherwise I'd just use the SRWLock that was introduced with Vista). I've written this custom ...
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Review a newbie's pthread code

I'm a pthread newbie and I've been giving myself a challenge: I want to have a resource that multiple threads can access at the same time as read. However, if a ...
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1answer
433 views

Single word CAS tagged pointer for algorithms susceptible to the ABA problem

I've been looking for a solution to the ABA problem for a lock-free stack. Searching the Web revealed patented and complicated hazard pointers and tagged pointers using double compare-and-swap (DCAS, ...
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101 views

Security concerns with locking files

I'm writing a perl script which reads logs from a file and looks for matches from another file before sending the matches off by email. The problem is, I'm dealing with files which could be changed (a ...
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2answers
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Using Timer with Backgroundworker to ensure the doWork method is called

I have a windows forms application in which a backgroundworker is called again and again. I need to avoid concurrent access of the code in dowork method for the backgroundWorker; but also need to ...
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4answers
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Associating a lock/mutex with the data it protects

I've recently come across some areas of code in our solution that have a few thread-safety problems. Thread-safety is a minefield at best so I thought I'd have an attempt at writing a few little ...
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1answer
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Waiting for a lock to release with ManualResetEvent and Quartz

Follow-up to: Waiting for a lock to release with Thread.Sleep()? I've found the time I tried to rewrite my WaitForLock-Method to utilize the Quartz.NET ...
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3answers
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Waiting for a lock to release with Thread.Sleep()?

There's a follow-up: Waiting for a lock to release with ManualResetEvent and Quartz. I've written a simple Lock-Mechanism which is saving the states of the locks in a database. Now I need to wait ...
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1answer
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Transactions and Locking in Rails 3

I am new to Rails and have a system that needs to process transactions. A user can enter a transaction to which one more users are tied. These users owe some amount of money to the person making the ...