Re: [PATCH v4 1/2] locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED flag

[Peter Zijlstra]

On Wed, May 16, 2018 at 12:48:30PM +0200, Oleg Nesterov wrote:
> > +static inline bool is_rwsem_owner_spinnable(struct task_struct *owner)
> >  {
> > -	return owner && owner != RWSEM_READER_OWNED;
> > +	return !((unsigned long)owner & RWSEM_ANONYMOUSLY_OWNED);
> >  }
> 
> Perhaps you should add __attribute__(aligned) to struct rw_semaphore then...
> 
> I don't think it is really needed, but see the comment under struct address_space.

Luckily we just dropped CRIS support, but yeah, who knows if some other
dodgy arch also doesn't properly align things.

>From a quick test, m68k is the only odd one, it seems to align pointers
on 2 bytes.