Distributed Reader-Writer Mutex by Dmitry Vyukov

[aminer10]

Hello all;

I have loolked at the Distributed Reader-Writer Mutex by Dmitry Vyukov, look at 

http://www.1024cores.net/home/lock-free-algorithms/reader-writer-problem/distributed-reader-writer-mutex


and i have looked at it and i think there is a problem with this method, cause look
at the write lock function:

int         distr_rw_mutex_wrlock           (distr_rw_mutex_t* mtx)
{
    int                     i;
    for (i = 0; i != mtx->proc_count; i += 1)
        pthread_rwlock_wrlock(&mtx->cell.mtx);
    return 0;
}


What is wrong with it ? suppose two or more writers wants to lock this distributed rwlock
there is a possibility of a deadlock.

So i think you have to use a critical section around the for loop to be able to lock
all the rwlocks at the same time to avoid the deadlock problem..


Am i correct or not ?


Thank you,
Amine Moulay Ramdane.

[aminer10]

I wrote:

> So i think you have to use a critical section around the for loop to be able
> to lock
> all the rwlocks at the same time to avoid the deadlock problem..

I mean  you have to use a critical section around the for loop to be able 
to lock all the rwlocks atomicly  to avoid the deadlock problem..

Thank you,

Amine Moulay Ramdane.

[aminer10]

Sorry for my english: i mean atomically.

Thank you,

Amine Moulay Ramdne.

[aminer10]

Patricia Shanahan wrote:

> The text explanation on the referenced web page says 'No additional
> synchronization between writers is required, writers acquire the mutexes
> in the same order (from 0 to P-1), so ownership over mutex 0 basically
> determines who is the "current" writer (all other potential writers are
> parked on mutex 0).'

You are absolutly right.

Thank you,

Amine Moulay Ramdane.

[aminer10]

Patricia Shanahan wrote:

> The text explanation on the referenced web page says 'No additional
> synchronization between writers is required, writers acquire the mutexes
> in the same order (from 0 to P-1), so ownership over mutex 0 basically
> determines who is the "current" writer (all other potential writers are
> parked on mutex 0).'

You are absolutly right.

Thank you,

Amine Moulay Ramdane.