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SubjectRe: [S+Q3 00/23] SLUB: The Unified slab allocator (V3)
On Tue, 17 Aug 2010, Christoph Lameter wrote:

> > Ok, so this is panicking because of the error handling when trying to
> > create sysfs directories with the same name (in this case, :dt-0000064).
> > I'll look into while this isn't failing gracefully later, but I isolated
> > this to the new code that statically allocates the DMA caches in
> > kmem_cache_init_late().
>
> Hmm.... Strange. The DMA caches should create a distinct pattern there.
>

They do after patch 11 when you introduce dynamically sized kmalloc
caches, but not after only patches 1-8 were applied. Since this wasn't
booting on my system, I bisected the problem to patch 8 where
kmem_cache_init_late() would create two DMA caches of size 64 bytes: one
becauses of kmalloc_caches[0] (kmem_cache_node) and one because of
kmalloc_caches[6] (2^6 = 64). So my fixes are necessary for patch 8 but
obsoleted later, and then the shared cache support panics on memset().

> > - the entire iteration in kmem_cache_init_late() needs to be protected by
> > slub_lock. The comment in create_kmalloc_cache() should be revised
> > since you're no longer calling it only with irqs disabled.
> > kmem_cache_init_late() has irqs enabled and, thus, slab_caches must be
> > protected.
>
> I moved it to kmem_cache_init() which is run when we only have one
> execution thread. That takes care of the issue and ensures that the dma
> caches are available as early as before.
>

I didn't know if that was a debugging patch for me or if you wanted to
push that as part of your series, I'm not sure if you actually need to
move it to kmem_cache_init() now that slub_state is protected by
slub_lock. I'm not sure if we want to allocate DMA objects between
kmem_cache_init() and kmem_cache_init_late().


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