Re: [PATCH] slub: Avoid irqoff/on in bulk allocation

[Christoph Lameter <cl@linux.com>]

On Wed, 2 Sep 2015, Jesper Dangaard Brouer wrote:

> > +error:
> > +	__kmem_cache_free_bulk(s, i, p);
>
> Don't we need to update "tid" here, like:
>
>   c->tid = next_tid(c->tid);
>
> Consider a call to the ordinary kmem_cache_alloc/slab_alloc_node was
> in-progress, which get PREEMPT'ed just before it's call to
> this_cpu_cmpxchg_double().
>  Now, this function gets called and we modify c->freelist, but cannot
> get all objects and then fail (goto error).  Although we put-back
> objects (via __kmem_cache_free_bulk) don't we want to update c->tid
> in-order to make sure the call to this_cpu_cmpxchg_double() retry?

Hmm... I thought that __kmem_cache_free_bulk is run with interrupts
disabled and will invoke the __slab_free which will increment tid if any
objects are freed from the local page.

That occurs before interrupts are reenabled.

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