Messages in this thread | | | Subject | Re: [mm][RFC][PATCH 0/11] mm accessor updates. | From | Peter Zijlstra <> | Date | Thu, 17 Dec 2009 21:19:27 +0100 |
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On Thu, 2009-12-17 at 14:13 -0600, Christoph Lameter wrote: > On Thu, 17 Dec 2009, Peter Zijlstra wrote: > > > > You always need some reference on the mm_struct (mm_read_lock) if you are > > > going to sleep to ensure that mm_struct still exists after waking up (page > > > fault, page allocation). RCU and other spin locks are not helping there. > > > > Depends what you go to sleep for, the page fault retry patches simply > > retook the whole fault and there is no way the mm could have gone away > > when userspace isn't executing. > > get_user_pages ?
on !current->mm that is? There's only very few cases for that, non of which are on a hot-path iirc.
> > Also pinning a page will pin the vma will pin the mm, and then you can > > always take explicit mm_struct refs, but you really want to avoid that > > since that's a global cacheline again. > > Incrementing a refcount on some random page wont protect you unless > mmap_sem is held.
Hmm, right, its pagetables I meant, but we can probably make it be true for locking a page.
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