linux-kernel - Re: [BUG] infinite loop in find_get

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Message-ID: <CA+55aFyF4Tr0BNXhuka2FjGAOn2oYoBvX=nUjueCvLezyf2XKQ@mail.gmail.com>
Date:	Tue, 13 Sep 2011 23:48:58 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] infinite loop in find_get_pages()

Again, sorry for the possible duplicates - but it looks like my email
hasn't been going out.

                      Linus

On Tue, Sep 13, 2011 at 6:26 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Tue, Sep 13, 2011 at 12:23 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>>
>> while :
>> do
>>  echo 3 >/proc/sys/vm/drop_caches
>>  sleep 20
>> done
>
> Btw, do you actually have problems without this?
>
> The drop_caches thing could potentially result in a livelock, where
> we're dropping stuff as we are reading it in, and the reader just
> never makes progress (because dropping things is always faster than
> reading).
>
> So it may not be a "true lockup", it may just be really *really* slow,
> and wasting tons of CPU.
>
> It is possible that we should look at modifying the drop_caches code
> so that it always makes forward progress..
>
>                            Linus
>
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