Subj : Re: recursive mutexes
To   : comp.programming.threads
From : David Schwartz
Date : Sun May 15 2005 01:06 pm


"Uenal Mutlu" <520001085531-0001@t-online.de> wrote in message 
news:d67npb$enc$01$1@news.t-online.com...

> Are you sure? Let's see:
>
> void X::f()
> {
>   Lock();
>   for (int i = 0; i < 1000; i++)
>     f();
>   Unlock();
> }
>
> void X::g()
> {
>  if (!IsLocked())
>    return;
>  //...do..something...
> }
>
> Are you saying the above version of g() is faster than this one:  ?
> void X::g()
> {
>  //...do..something...
> }

    I never argued the performance issue. But here's a more realistic 
example:

    Without recursive mutexes:

protected:

f_locked(void)
{ // call with mutex locked
 DoStuff();
}

public:

f(void)
{ // call with mutex unlocked
 Lock();
 f_locked();
 Unlock();
}

many_f(void)
{ // call with mutex unlocked
 Lock();
 for(int i=0; i<1000; i++) f_locked();
 Unlock();
}

With recursive mutex:

public:

f(void)
{ // call with mutex in any state
 Lock();
 DoStuff();
 Unlock();
}

many_f(void)
{ // call with mutex in any state
 Lock();
 for(int i=0; i<1000; i++) f();
 Unlock();
}

    Which do you think is faster?

    DS

.