Implementing Cond variable using atomic operations

[shay86]

I'm using atomic operations to implement mutex and cond (i'm currenting using threadpool using posix threads and now need to move to tbb).

For example i'm doing something like this:

Lock_mutex (mutex * m){

while (T&S(TS_Object *) m);

}

Unlock_mutex(mutex *m){

Reset((TS_Object *) m)

}

(this is just pseudo code, the param is actually an atomic operation).

My problem is with implementing pthread_cond_wait and pthread_cond_signal

using only T&S or C&S.

Can anyone directs me please?

Thanks in advanced,

Shay.

[shay86]

This is actually the functions for T&S:

T&S (T&S_object * TS)

{

If (TS.flag==false) {

TS.flag = true;

return false;

} else return true;

}

Reset (T&S_object * TS)

{

TS.flag=false;

}

[Dmitry_Vyukov]

Real-world condition variables usually block threads. Blocking can't be implemented with atomic operations.
If you need only a toy implementation, then you can implement wait() as unlock-yield-lock, and signal() as no op. No need for atomic operations either.

[shay86]

Thanks for the really fast reply,

i'm not familiar with unlock-yield-lock, can you link me to a code example maybe?

and also, how can i signal other threads in my threadpool that a job is done if i made this function no op?

Thanks.

[Dmitry_Vyukov]

> i'm not familiar with unlock-yield-lock, can you link me to a code example maybe?

void condvar_wait(mutex* m)
{

Unlock_mutex(m);

pthread_yield()/SwitchToThread();

Lock_mutex(m);

}

void condvar_signal/broadcast()
{
}

[Dmitry_Vyukov]

> and also, how can i signal other threads in my threadpool that a job is done if i made this function no op?

Since threads are not blocked, there is no need to signal them - they are always ready notice any state change.

[shay86]

Excellent, thanks a lot.

Is there anequivalent for pthread_yield in tbb's library?

or i should implement one myself?

Thanks.

[Dmitry_Vyukov]

Quoting shay86

Excellent, thanks a lot.

Is there anequivalent for pthread_yield in tbb's library?

or i should implement one myself?

Thanks.

tbb::this_tbb_thread::yield() in

[RafSchietekat]

Has anyone tried emulating condition variables with dummy child tasks and continuations?

[Vladimir_P_1234567890]

don't you want to use tbb's condition variable?

--Vladimir