Re: linux-next: build failure after merge of the rcu tree

Paul E. McKenney
2017-03-08T17:40:13Z

On Wed, Mar 08, 2017 at 11:13:38AM +0100, Daniel Vetter wrote:
> On Wed, Mar 08, 2017 at 12:16:45PM +1100, Stephen Rothwell wrote:
> > Hi Paul,
> >
> > After merging the rcu tree, today's linux-next build (x86_64 allmodconfig)
> > failed like this:
> >
> > In file included from include/linux/resource_ext.h:19:0,
> > from include/linux/pci.h:32,
> > from include/drm/drmP.h:50,
> > from drivers/gpu/drm/i915/i915_gem.c:28:
> > drivers/gpu/drm/i915/selftests/mock_gem_device.c: In function 'mock_gem_device':
> > drivers/gpu/drm/i915/selftests/mock_gem_device.c:177:9: error: 'SLAB_DESTROY_BY_RCU' undeclared (first use in this function)
> > SLAB_DESTROY_BY_RCU);
> > ^
> > include/linux/slab.h:149:4: note: in definition of macro 'KMEM_CACHE'
> > (__flags), NULL)
> > ^
> > drivers/gpu/drm/i915/selftests/mock_gem_device.c:177:9: note: each undeclared identifier is reported only once for each function it appears in
> > SLAB_DESTROY_BY_RCU);
> > ^
> > include/linux/slab.h:149:4: note: in definition of macro 'KMEM_CACHE'
> > (__flags), NULL)
> > ^
> > /
> >
> > Caused by commit
> >
> > 24b7cb25b8d1 ("mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU")
>
> Awesome rename. Count us in among the people who first thought this
> provides more guarantees than it does.

Glad you like it! ;-)

> > interacting with commit
> >
> > 0daf0113cff6 ("drm/i915: Mock infrastructure for request emission")
> >
> > from the drm-intel tree.
> >
> > I added the following merge fix patch:
> >
> > From: Stephen Rothwell <sfr@canb.auug.org.au>
> > Date: Wed, 8 Mar 2017 12:09:49 +1100
> > Subject: [PATCH] drm/i915: merge fix for "mm: Rename SLAB_DESTROY_BY_RCU to
> > SLAB_TYPESAFE_BY_RCU"
> >
> > Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
>
> Should we handle this with a topic branch? It's trivial to resolve, but I
> fear the note that this conflict exists might get lost somewhere between
> now and when the drm pull lands in Linus' inbox in 2 months ...
>
> Otoh he's probably going to compile test drm extra carefully and will
> notice :-)

If it gets too ugly, I can always allow both SLAB_TYPESAFE_BY_RCU
and SLAB_DESTROY_BY_RCU as synonyms in 4.12, and then remove
SLAB_DESTROY_BY_RCU in 4.13.

Thanx, Paul

> -Daniel
>
> > ---
> > drivers/gpu/drm/i915/selftests/mock_gem_device.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/selftests/mock_gem_device.c b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
> > index 6a8258eacdcb..9f24c5da3f8d 100644
> > --- a/drivers/gpu/drm/i915/selftests/mock_gem_device.c
> > +++ b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
> > @@ -174,7 +174,7 @@ struct drm_i915_private *mock_gem_device(void)
> > i915->requests = KMEM_CACHE(mock_request,
> > SLAB_HWCACHE_ALIGN |
> > SLAB_RECLAIM_ACCOUNT |
> > - SLAB_DESTROY_BY_RCU);
> > + SLAB_TYPESAFE_BY_RCU);
> > if (!i915->requests)
> > goto err_vmas;
> >
> > --
> > 2.11.0
> >
> > --
> > Cheers,
> > Stephen Rothwell
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
>

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