On 26. 12. 22, 7:21, 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.
Really? (see below)
--- a/drivers/tty/serial/dz.c
+++ b/drivers/tty/serial/dz.c
...
@@ -687,23 +686,19 @@ static int dz_map_port(struct uart_port *uport)
static int dz_request_port(struct uart_port *uport)
{
struct dz_mux *mux = to_dport(uport)->mux;
- int map_guard;
int ret;
- map_guard = atomic_add_return(1, &mux->map_guard);
- if (map_guard == 1) {
- if (!request_mem_region(uport->mapbase, dec_kn_slot_size,
- "dz")) {
- atomic_add(-1, &mux->map_guard);
- printk(KERN_ERR
- "dz: Unable to reserve MMIO resource\n");
+ refcount_inc(&mux->map_guard);
+ if (refcount_read(&mux->map_guard) == 1) {
This is now racy, right?
thanks,
--
js
suse labs
