linux-kernel - Re: X-freeze after clflush changes [Was: 2.6.23-rc6-mm1]

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Message-Id: <20070919121017.0cbcbc30.akpm@linux-foundation.org>
Date:	Wed, 19 Sep 2007 12:10:17 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>
Subject: Re: X-freeze after clflush changes [Was: 2.6.23-rc6-mm1]

On Wed, 19 Sep 2007 16:59:04 +0200 Jiri Slaby <jirislaby@...il.com> wrote:

> ---------8<---------8<---------8<---------8<---------8<---------8<----
> That means
> void agp_generic_destroy_page(void *addr)
> {
>         struct page *page;
> 
>         if (addr == NULL)
>                 return;
> 
>         page = virt_to_page(addr);
> (1)     unmap_page_from_agp(page);
>         put_page(page);
> (2)     free_page((unsigned long)addr);
>         atomic_dec(&agp_bridge->current_memory_agp);
> }
> 
> (1) unmap_page_from_agp -> change_page_attr -> change_page_attr_addr ->
> __change_page_attr -> save_page -> list_add(&fpage->lru, &deferred_pages);
> (2) free_page -> free_pages -> __free_pages -> free_hot_page ->
> free_hot_cold_page -> list_add(&page->lru, &pcp->list);

that'll hurt.

> any ideas how to fix this?

We should hold a single reference on the page for its membership in
deferred_pages.
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