linux-kernel - Re: x86_64: potential critical issue with quicklists and page table pages

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Message-ID: <alpine.LFD.0.999.0709211139550.16478@woody.linux-foundation.org>
Date:	Fri, 21 Sep 2007 11:48:55 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
cc:	clameter@....com, akpm@...ux-foundation.org, ak@...e.de,
	linux-kernel@...r.kernel.org, tony.luck@...el.com,
	asit.k.mallick@...el.com
Subject: Re: x86_64: potential critical issue with quicklists and page table
 pages



On Fri, 21 Sep 2007, Siddha, Suresh B wrote:
>
> git commit 34feb2c83beb3bdf13535a36770f7e50b47ef299 started using quicklists
> for freeing page table pages and removed the usage of tlb_remove_page()
> 
> And looking at quicklist_free() and quicklist_free_page(), on a NUMA platform,
> this can potentially free the page before the corresponding TLB caches
> are flushed.

Hmm? We only add them to the quicklists in the exact same places where we 
*used* to just free them entirely. So I don't see why semantics would have 
changed..

> Can we revert this commit for 2.6.23 and look at this code post 2.6.23?

I'll happily revert it, but I want to understand this better, so more of 
an explanation of the codepath that actually does something wrong, please.

		Linus
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