Re: [ckrm-tech] [PATCH 4/6] CKRM: Add guarantee support for mem controller

[Dave Hansen <haveblue@us.ibm.com>]

On Thu, 2005-06-30 at 11:11 -0700, Chandra Seetharaman wrote:
> On Thu, 2005-06-30 at 14:52 +0900, YAMAMOTO Takashi wrote:
> > > +static inline void
> > > +ckrm_clear_page_class(struct page *page)
> > > +{
> > > +	struct ckrm_zone *czone = page_ckrmzone(page);
> > > +	if (czone == NULL)
> > > +		return;
> > > +	sub_use_count(czone->memcls, 0, page_zonenum(page), 1);
> > > +	kref_put(&czone->memcls->nr_users, memclass_release);
> > > +	set_page_ckrmzone(page, NULL);
> > >  }
> > 
> > are you sure if it's safe?
> > this function is called with zone->lock held,
> > and memclass_release calls kfree.
> 
> i don't understand why you think it is a problem to call kfree with lock
> held( i agree calling kmalloc with wait flag when a lock is being held
> is not correct).

kfree->__cache_free
	->cache_flusharray
	->free_block
	->slab_destroy
	->kmem_freepages
	->free_pages
	->__free_pages
	->__free_pages_ok
	->free_pages_bulk:

	spin_lock_irqsave(&zone->lock, flags);

Deadlock.

Whew!!!

-- Dave

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