linux-kernel - Re: [GIT] Sparc

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Message-ID: <CA+55aFzXDxicQRZNEDaLruxackq-6NkkYk5gM1L6Ak38ggJKrQ@mail.gmail.com>
Date:	Mon, 23 Mar 2015 10:12:30 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Miller <davem@...emloft.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	sparclinux@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT] Sparc

On Mon, Mar 23, 2015 at 10:05 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Mon, Mar 23, 2015 at 9:55 AM, David Miller <davem@...emloft.net> wrote:
>>
>> Some perf bug fixes from David Ahern, and the fix for that nasty
>> memmove() bug.
>
> That doesn't seem to be marked for stable? Or do you do the same thing
> as for networking, and just collect stable patches manually?

Side note: the memmove commit message is a bit misleading. The old
code handled zero-length calls fine, even if it wasn't explicit: it
always called memmove() for that case.

The condition "dst <= src || src + len <= dst" ends up being always
true when len is zero (because it obviously ends up being "dst <= src
|| src <= dst").

So there was just one bug - the 64-byte overlap with the cacheline
establish for the destination. Even that cacheline establish would
have been ok if all the loads for the 64-byte block had been done
up-front.

Oh well. I'm actually somewhat surprised this didn't hit anything
else. Doesn't networking also end up doing overlapping memmove() on
the skb data occasionally?

                       Linus
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