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Date: Sat, 13 Jun 2009 07:44:13 +1000
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
To: Pekka J Enberg <penberg@...helsinki.fi>
Cc: linux-kernel@...r.kernel.org, mingo@...e.hu,
torvalds@...ux-foundation.org, cl@...ux-foundation.org,
akpm@...ux-foundation.org, npiggin@...e.de
Subject: Re: [PATCH 2/3] slab,slub: don't enable interrupts during early
boot
On Fri, 2009-06-12 at 18:41 +0300, Pekka J Enberg wrote:
> From: Pekka Enberg <penberg@...helsinki.fi>
>
> As explained by Benjamin Herrenschmidt:
>
> Oh and btw, your patch alone doesn't fix powerpc, because it's missing
> a whole bunch of GFP_KERNEL's in the arch code... You would have to
> grep the entire kernel for things that check slab_is_available() and
> even then you'll be missing some.
>
> For example, slab_is_available() didn't always exist, and so in the
> early days on powerpc, we used a mem_init_done global that is set form
> mem_init() (not perfect but works in practice). And we still have code
> using that to do the test.
>
> Therefore, mask out __GFP_WAIT in the slab allocators in early boot code to
> avoid enabling interrupts.
Ack. I would also like to see that pushed down to page_alloc.c but
that's another discussion at this stage :-) (suspend/resume will need
that if we start using the mechanism to mask out FS and IO).
Cheers,
Ben.
> Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>
> ---
> include/linux/gfp.h | 3 +++
> include/linux/slab.h | 2 ++
> include/linux/slob_def.h | 5 +++++
> include/linux/slub_def.h | 2 ++
> init/main.c | 1 +
> mm/slab.c | 22 ++++++++++++++++++++++
> mm/slub.c | 16 ++++++++++++++++
> 7 files changed, 51 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 0bbc15f..ec0fede 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -85,6 +85,9 @@ struct vm_area_struct;
> __GFP_NOWARN|__GFP_REPEAT|__GFP_NOFAIL|\
> __GFP_NORETRY|__GFP_NOMEMALLOC)
>
> +/* Control slab gfp mask during early boot */
> +#define SLAB_GFP_BOOT_MASK __GFP_BITS_MASK & ~(__GFP_WAIT|__GFP_IO|__GFP_FS);
> +
> /* Control allocation constraints */
> #define GFP_CONSTRAINT_MASK (__GFP_HARDWALL|__GFP_THISNODE)
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 4880306..219b8fb 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -319,4 +319,6 @@ static inline void *kzalloc_node(size_t size, gfp_t flags, int node)
> return kmalloc_node(size, flags | __GFP_ZERO, node);
> }
>
> +void __init kmem_cache_init_late(void);
> +
> #endif /* _LINUX_SLAB_H */
> diff --git a/include/linux/slob_def.h b/include/linux/slob_def.h
> index 0ec00b3..bb5368d 100644
> --- a/include/linux/slob_def.h
> +++ b/include/linux/slob_def.h
> @@ -34,4 +34,9 @@ static __always_inline void *__kmalloc(size_t size, gfp_t flags)
> return kmalloc(size, flags);
> }
>
> +static inline void kmem_cache_init_late(void)
> +{
> + /* Nothing to do */
> +}
> +
> #endif /* __LINUX_SLOB_DEF_H */
> diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
> index be5d40c..4dcbc2c 100644
> --- a/include/linux/slub_def.h
> +++ b/include/linux/slub_def.h
> @@ -302,4 +302,6 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
> }
> #endif
>
> +void __init kmem_cache_init_late(void);
> +
> #endif /* _LINUX_SLUB_DEF_H */
> diff --git a/init/main.c b/init/main.c
> index b3e8f14..f6204f7 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -640,6 +640,7 @@ asmlinkage void __init start_kernel(void)
> "enabled early\n");
> early_boot_irqs_on();
> local_irq_enable();
> + kmem_cache_init_late();
>
> /*
> * HACK ALERT! This is early. We're enabling the console before
> diff --git a/mm/slab.c b/mm/slab.c
> index cd76964..6c0c4df 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -304,6 +304,12 @@ struct kmem_list3 {
> };
>
> /*
> + * The slab allocator is initialized with interrupts disabled. Therefore, make
> + * sure early boot allocations don't accidentally enable interrupts.
> + */
> +static gfp_t slab_gfp_mask __read_mostly = SLAB_GFP_BOOT_MASK;
> +
> +/*
> * Need this for bootstrapping a per node allocator.
> */
> #define NUM_INIT_LISTS (3 * MAX_NUMNODES)
> @@ -1654,6 +1660,14 @@ void __init kmem_cache_init(void)
> */
> }
>
> +void __init kmem_cache_init_late(void)
> +{
> + /*
> + * Interrupts are enabled now so all GFP allocations are safe.
> + */
> + slab_gfp_mask = __GFP_BITS_MASK;
> +}
> +
> static int __init cpucache_init(void)
> {
> int cpu;
> @@ -3237,6 +3251,10 @@ retry:
> }
>
> if (!obj) {
> + /* Lets avoid crashing in early boot code. */
> + if (WARN_ON_ONCE((local_flags & ~slab_gfp_mask) != 0))
> + local_flags &= slab_gfp_mask;
> +
> /*
> * This allocation will be performed within the constraints
> * of the current cpuset / memory policy requirements.
> @@ -3354,6 +3372,8 @@ __cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
> unsigned long save_flags;
> void *ptr;
>
> + flags &= slab_gfp_mask;
> +
> lockdep_trace_alloc(flags);
>
> if (slab_should_failslab(cachep, flags))
> @@ -3434,6 +3454,8 @@ __cache_alloc(struct kmem_cache *cachep, gfp_t flags, void *caller)
> unsigned long save_flags;
> void *objp;
>
> + flags &= slab_gfp_mask;
> +
> lockdep_trace_alloc(flags);
>
> if (slab_should_failslab(cachep, flags))
> diff --git a/mm/slub.c b/mm/slub.c
> index 3964d3c..30354bf 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -178,6 +178,12 @@ static enum {
> SYSFS /* Sysfs up */
> } slab_state = DOWN;
>
> +/*
> + * The slab allocator is initialized with interrupts disabled. Therefore, make
> + * sure early boot allocations don't accidentally enable interrupts.
> + */
> +static gfp_t slab_gfp_mask __read_mostly = SLAB_GFP_BOOT_MASK;
> +
> /* A list of all slab caches on the system */
> static DECLARE_RWSEM(slub_lock);
> static LIST_HEAD(slab_caches);
> @@ -1595,6 +1601,8 @@ static __always_inline void *slab_alloc(struct kmem_cache *s,
> unsigned long flags;
> unsigned int objsize;
>
> + gfpflags &= slab_gfp_mask;
> +
> lockdep_trace_alloc(gfpflags);
> might_sleep_if(gfpflags & __GFP_WAIT);
>
> @@ -3104,6 +3112,14 @@ void __init kmem_cache_init(void)
> nr_cpu_ids, nr_node_ids);
> }
>
> +void __init kmem_cache_init_late(void)
> +{
> + /*
> + * Interrupts are enabled now so all GFP allocations are safe.
> + */
> + slab_gfp_mask = __GFP_BITS_MASK;
> +}
> +
> /*
> * Find a mergeable slab cache
> */
--
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