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SubjectRe: [tip:urgent] fix kfifo_out_locked race bug
On Tue, 05 Jan 2010 14:38:35 +0100
Stefani Seibold <stefani@seibold.net> wrote:

> This patch fix a wrong optimization in include/linux/kfifo.h which could
> cause a race in kfifo_out_locked.
>
> Please apply it to the 2.6.33-rc* tree.
>
> Signed-off-by: Stefani Seibold <stefani@seibold.net>
> ---
> kfifo.h | 7 -------
> 1 file changed, 7 deletions(-)
>
> --- linux-2.6.33-rc2.orig/include/linux/kfifo.h 2009-12-27
> 23:37:04.921185257 +0100
> +++ kfifo.h 2010-01-05 14:32:31.414316321 +0100
> @@ -228,13 +228,6 @@ static inline __must_check unsigned int
>
> ret = kfifo_out(fifo, to, n);
>
> - /*
> - * optimization: if the FIFO is empty, set the indices to 0
> - * so we don't wrap the next time
> - */
> - if (kfifo_is_empty(fifo))
> - kfifo_reset(fifo);
> -
> spin_unlock_irqrestore(lock, flags);
>
> return ret;
>

Thanks. Some nits:

- the patch is wordwrapped. I fixed that up.

- you removed the cc's of the particpants in the earlier dicsussion.
I restored them here.

- the changelog didn't describe the bug - what was the race??

- I added "Reported-by: Johan Hovold <jhovold@gmail.com>" to the changelog

- the "[tip:urgent]" tag in the Subject: line is something which
Ingo's patch tools add to outgoing email notifications and wasn't
appropriate here. Plain old "[patch]" would be typical.



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