On Thu, Jul 24, 2014 at 05:17:01PM +0800, xinhui.pan wrote:
> If the gsmtty is still used by some process, we could not just
> simply clear gsm_mux[gsm->num]. Clear it when gsm is being free.
> Otherwise we will hit crashes when userspace close the gsmtty.
>
> Also add gsm_mux_get() and gsm_mux_put() to make gsm_mux[] is used safely.
> We can do activation/deactivation with same gsm more than once now.
> This is for fixing the FIXME.
>
> Signed-off-by: xinhui.pan <[email protected]>
> Reviewed-by: Zhang Yanmin <[email protected]>
> ---
> drivers/tty/n_gsm.c | 84
> ++++++++++++++++++++++++++++++++++++---------------
> 1 file changed, 60 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index 81e7ccb..290df56 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -2020,6 +2020,58 @@ static void gsm_error(struct gsm_mux *gsm,
> }
>
> /**
> + * gsm_mux_get - get/fill one entry in gsm_mux
> + * @gsm: our gsm
> + *
> + * Although its name end with get, it don't inc ref-count actually.
Then don't call it a 'get' function :(
> + * get one entry is just like fill pte, first memory access will
> + * cause page_fault, the next accesses don't. So do here.
This doesn't make much sense to me, can you please explain it better?
> + */
> +
blank line?
> +static int gsm_mux_get(struct gsm_mux *gsm)
> +{
> + int i;
> +
> + if (gsm->num >= MAX_MUX) /* gsm is alloc by kzalloc, just be careful */
> + return -EIO;
-EIO?
> + if (gsm_mux[gsm->num] == gsm) /* We have already set gsm->num */
> + return 0;
> +
> + spin_lock(&gsm_mux_lock);
> + for (i = 0; i < MAX_MUX; i++) {
> + if (gsm_mux[i] == NULL) {
> + gsm->num = i;
> + gsm_mux[i] = gsm;
> + break;
> + }
> + }
> + spin_unlock(&gsm_mux_lock);
> +
> + if (i == MAX_MUX)
> + return -EBUSY;
> + return 0;
> +}
> +
> +/**
> + * gsm_mux_put - put/clear one entry in gsm_mux
> + * @gsm: our gsm
> + *
> + * Although its name end with put, it don't dec ref-count actually.
> + * put one entry is just like clear pte, So do here.
> + */
> +
> +static void gsm_mux_put(struct gsm_mux *gsm)
> +{
> + if (gsm->num >= MAX_MUX)
> + return;
> +
> + spin_lock(&gsm_mux_lock);
> + if (gsm_mux[gsm->num] == gsm)
How can this not be true?
> + gsm_mux[gsm->num] = NULL;
> + spin_unlock(&gsm_mux_lock);
> +}
Why can't you do dynamic reference counting of your structure, that
would allow you to get rid of your global array, right?
thanks,
greg k-h
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