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RWRecMutex

xdm
xdm La Coruña, Spain
in Help Center
Hello i have a problem with RWRecMutex

for example if i have the next slice definition
           interface Reader
           {
                      nonmutating double getAmount();
           }

           interface Writer
           {
                     idempotent doSameThing();
           }

           class A implements Writer,Reader
           {
                       double total;
                       dobule rest;
           }

and the c++ implementation 
class AI : virtual public A
{
                 virtual doSameThing(const Ice::Current& current);
                 virtual getAmount(const Ice::Current& current)const;
}
in cpp file
AI::getAmount(const Ice::Current& const)const
{
      IceUtil::RWRecMutes::RLock sync(this);
      return total-rest;
}

 AI::doSameThing(const Ice::Current& current)
 {
        IceUtil::RWRecMutex::WLock sync(this);
        if(getAmount()>0)           //Server blocked at this point 
                     rest++;
}

Is normal that the servers block here because i invoke a Read opeation inside a Write operation. In this example can be solved easy with chage the code of getAmount to the doSameThing but this solution don't scale well.

how can aboid this ?

thanks in adavantage

Comments

  • matthew
    matthew NL, Canada
    xdm wrote:
    ...

    Is normal that the servers block here because i invoke a Read opeation inside a Write operation. In this example can be solved easy with chage the code of getAmount to the doSameThing but this solution don't scale well.

    how can aboid this ?

    thanks in adavantage

    Its intended that you cannot acquire a read lock while you hold a write lock. This is illegal, and has undefined behaviour. This is the same semantics as POSIX threads. Its arguable whether hanging is nice though :)

    In this case its pretty easy to rearrange your code to use some internal method that doesn't acquire a lock. Then call the internal method from the external methods.

    Regards, Matthew

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