On Wed, Jun 19, 2013 at 07:39:15PM +0000, Miod Vallat wrote:
> > > > - p->p_sigmask = mask &~ sigcantmask;
> > > > + p->p_sigmask = mask;
> >
> > On the right architecture where a word store isn't atomic enough and
> > with the right compiler that decides to put p_sigmask on an address
> > ending with 0xFFF with 4k-sized pages, we have two problems already.
>
> Holy Pumpkin forbid, struct proc layout is sane enough for fields to be
> aligned to their natural alignment, and the allocator will return
> properly aligned structs as well.
>
> > I'm only asking if such a situation can happen, or if there is some
> > ensure_this_assignment_is_always_atomic(&p->p_sigmask, mask); function
> > that I missed.
>
> If such a function exists, it should be shot, if only for having a too
> long name.
>
> Miod
But watch out, as kettenis@ already mentioned elsewhere, this can only
be safe if *all* reads and modifications to the mask are done in an
atomic way.
Straight read and assignment of int values is safe, afaik, but e.g.
struct assignment and memcpy are *not* atomic.
-Otto
