[ofa-general] Re: [PATCH] mmu notifiers #v6

[Andrea Arcangeli]

On Wed, Feb 20, 2008 at 08:41:55AM -0600, Robin Holt wrote:
> On Wed, Feb 20, 2008 at 11:39:42AM +0100, Andrea Arcangeli wrote:
> > XPMEM simply can't use RCU for the registration locking if it wants to
> > schedule inside the mmu notifier calls. So I guess it's better to add
> 
> Whoa there.  In Christoph's patch, we did not use rcu for the list.  It
> was a simple hlist_head.  The list manipulations were done under
> down_write(&current->mm->mmap_sem) and would therefore not be racy.  All
> the callout locations are already acquiring the mmap_sem at least
> readably, so we should be safe.  Maybe I missed a race somewhere.

You missed quite a few, see when atomic=1 and when mmu_rmap_notifier
is invoked for example.