On Sat, Dec 24, 2022 at 10:25:58PM +0530, Deepak R Varma wrote:
> The refcount_* APIs are designed to address known issues with the
> atomic_t APIs for reference counting. They provide following distinct
> advantages:
> - protect the reference counters from overflow/underflow
> - avoid use-after-free errors
> - provide improved memory ordering guarantee schemes
> - neater and safer.
> Hence, replace the atomic_* APIs by their equivalent refcount_t
> API functions.
>
> This patch proposal address the following warnings generated by
> the atomic_as_refcounter.cocci coccinelle script
> atomic_add_return(-1, ...)
>
> Signed-off-by: Deepak R Varma <drv@xxxxxxxxx>
> ---
>
> Changes in v2:
> 1. Separate the combined change into one variable per patch as
> suggested by gregkh@xxxxxxxxxxxxxxxxxxx
> 2. There was additional feedback on validating the change as it appeared to
> modify the existing logic. However, I found that the logic does not
> change with the proposed refcount_* APIs used in this change. Hence that
> feedback is not applied in this version.
>
> Please Note:
> The patch is compile tested using dec_station.defconfig for MIPS architecture.
>
> drivers/tty/serial/zs.c | 14 +++++---------
> drivers/tty/serial/zs.h | 2 +-
> 2 files changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/tty/serial/zs.c b/drivers/tty/serial/zs.c
> index 730c648e32ff..6be9933eff5c 100644
> --- a/drivers/tty/serial/zs.c
> +++ b/drivers/tty/serial/zs.c
> @@ -753,17 +753,15 @@ static int zs_startup(struct uart_port *uport)
> struct zs_port *zport = to_zport(uport);
> struct zs_scc *scc = zport->scc;
> unsigned long flags;
> - int irq_guard;
> int ret;
>
> - irq_guard = atomic_add_return(1, &scc->irq_guard);
> - if (irq_guard == 1) {
> + refcount_inc(&scc->irq_guard);
> + if (refcount_read(&scc->irq_guard) == 1) {
This conversion is wrong :(
