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c#multithreadingsynchronization
Karim
Karim

Reputation: 6283

is it possible to let the lock{} or similar structure lock on writes only?

well i mean i have several sections of code that use some variable i want to protect. but the idea is that several threads only read that variable. and only one threads is writing to it and it does that not that frequetly. i want to be able to let multiple threads do reading at the same time and only lock this varialbe when the the writing thread is accessing it.

if i use the normal lock(variable){} construct then all the reading threads will be blocked on each other. so is there a way to do that?

Upvotes: 2

Views: 129

Answers (2)

Henk Holterman
Henk Holterman

Reputation: 273169

If your variable is a simple value (an int), you can use System.Threading.Interlocked, like this:

int counter = 0;
void Worker1()
{        
    if (counter < 5)  // read is safe
    {
        Interlocked.Increment(ref counter); // write
        // ...
    }            
}

Notes

  • counter does not has to be volatile.
  • if you use long, read with Interlocked.Read()
  • if your 'variable' is an object, use ReaderWriterLockSlim or maybe just stick with lock() { }

Upvotes: 1

Greg Hewgill
Greg Hewgill

Reputation: 992707

It sounds like you're looking for the ReaderWriterLock class.

ReaderWriterLock is used to synchronize access to a resource. At any given time, it allows either concurrent read access for multiple threads, or write access for a single thread. In a situation where a resource is changed infrequently, a ReaderWriterLock provides better throughput than a simple one-at-a-time lock, such as Monitor.

Upvotes: 5

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