How to find all the tasks with a Sys V shm?

["Kamran Karimi" <kamrankarimi@hotmail.com>]

Hello all,

In 2.2 kernels one could access the vma segments of a Sys V shared memory 
(shm) through:
shp->attaches. In 2.6 kernels a shm is managed through a file. The question 
is: given a Sys V  key value, how can we find all the tasks that have 
attached the corresponding shm?

We can do the following (with error checking ignored):

    id = ipc_findkey(&shm_ids, key);
    shp = shm_lock(id);

    tsk = find_task_by_pid(shp->shm_cprid);

    vma = tsk->mm->mmap;
    while(vma) {
                 if(vma->vm_file == shp->shm_file)
                  break;
                 vma = vma->vm_next;
    }
    shm_unlock(shp);

But here we only get the vma of the task that created the shm, and not any 
other task who has attached it.

How can we find all the vma structures that represent a shm?

-Kamran