[CRIU] Re: [PATCH cr 6/6] restore: restore pocesses which share one fdtable

[Andrew Vagin]

> > -	if (prepare_fds(current))
> > -		return -1;
> > +	list_for_each_entry(child, &current->children, list) {
> > +		if (child->state == TASK_HELPER)
> > +			continue;
> > +		futex_wait_while_lt(&child->rst->fdt_lock, FDT_LOCK_SYNC);

Here we are waiting while all children. It's incorrect, because we should wait
only children who share fdtable. I will fix that.

> > +	}
> > +	futex_set_and_wake(&current->rst->fdt_lock, FDT_LOCK_SYNC);

A child wakes up a parent, that it is waiting fdtable and doing nothing else.
The child can not use file descriptors while fdtable is restored, so we
need this synchronization.

> > +
> > +	if (!shared_fdtable(current)) {
> > +		if (prepare_fds(current))
> > +			return -1;
> > +	} else
> > +		futex_wait_while_lt(&current->parent->rst->fdt_lock, FDT_LOCK_DONE);

Here we are waiting while fdtable is restored.

> > +	futex_set_and_wake(&current->rst->fdt_lock, FDT_LOCK_DONE);

fdtable was restored, children can continue

> 
> This looks too complicated and not correct. Plz, explain what is going on here.

> 
> >  	if (prepare_fs(pid))
> >  		return -1;