Re: [PATCH] pps: locking scheme fix up for PPS_GETPARAMS.
From: Andrew Morton
Date: Mon Nov 02 2009 - 20:54:25 EST
On Sat, 31 Oct 2009 17:03:23 +0100
Rodolfo Giometti <giometti@xxxxxxxx> wrote:
> Signed-off-by: Rodolfo Giometti <giometti@xxxxxxxx>
> Tested-by: Reg Clemens <clemens@xxxxxxx>
Please don't send unchangelogged patches.
> diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
> index fea17e7..ca5183b 100644
> --- a/drivers/pps/pps.c
> +++ b/drivers/pps/pps.c
> @@ -71,9 +71,14 @@ static long pps_cdev_ioctl(struct file *file,
> case PPS_GETPARAMS:
> pr_debug("PPS_GETPARAMS: source %d\n", pps->id);
> - /* Return current parameters */
> - err = copy_to_user(uarg, &pps->params,
> - sizeof(struct pps_kparams));
> + spin_lock_irq(&pps->lock);
> + /* Get the current parameters */
> + params = pps->params;
> + spin_unlock_irq(&pps->lock);
> + err = copy_to_user(uarg, ¶ms, sizeof(struct pps_kparams));
> if (err)
> return -EFAULT;
OK, I can see what the patch does and I can guess what sort of
situations would trigger it. But that's really not good enough.
Put yourself in the position of someone who is hitting a PPS bug and
wants to work out if your patch might fix it. Because the patch fails
to describe the user-visible symptoms (ie: the bug) then that person is
in the dark.
Also, someone (ie: me) needs to decide if this fix is to be backported
into earlier kernels. With no description of the end-user impact, how
can I possibly do that?
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