From: Jiri Slaby <jirislaby@kernel.org>
To: Deepak R Varma <drv@mailo.com>,
"Maciej W. Rozycki" <macro@orcam.me.uk>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Saurabh Singh Sengar <ssengar@microsoft.com>,
Praveen Kumar <kumarpraveen@linux.microsoft.com>
Subject: Re: [PATCH v4 1/2] tty: serial: dz: convert atomic_* to refcount_* APIs for map_guard
Date: Tue, 3 Jan 2023 09:59:52 +0100 [thread overview]
Message-ID: <e42d5d19-7ed5-468b-98cc-13d0187dc555@kernel.org> (raw)
In-Reply-To: <d85c7441b96ce387d9010142efc3469d53b6aedc.1671898144.git.drv@mailo.com>
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
next prev parent reply other threads:[~2023-01-03 9:00 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-24 16:32 [PATCH v3 0/2] tty: serial: dz: convert atomic_* to refcount_* Deepak R Varma
2022-12-24 16:33 ` [PATCH v3 1/2] tty: serial: dz: convert atomic_* to refcount_* APIs for map_guard Deepak R Varma
2022-12-26 6:21 ` [PATCH v4 " Deepak R Varma
2023-01-03 8:59 ` Jiri Slaby [this message]
2023-01-03 10:05 ` Deepak R Varma
2023-01-04 8:28 ` Greg Kroah-Hartman
2023-01-04 8:59 ` Deepak R Varma
2023-01-10 6:19 ` Deepak R Varma
2023-01-10 7:27 ` Reshetova, Elena
2023-01-10 7:47 ` Deepak R Varma
2023-01-10 7:57 ` Greg Kroah-Hartman
2022-12-24 16:34 ` [PATCH 2/2] tty: serial: dz: convert atomic_* to refcount_* APIs for irq_guard Deepak R Varma
2022-12-26 6:21 ` [PATCH v4 " Deepak R Varma
2023-01-03 9:00 ` Jiri Slaby
2023-01-03 10:09 ` Deepak R Varma
2023-01-04 8:28 ` Greg Kroah-Hartman
2023-01-04 9:00 ` Deepak R Varma
2022-12-26 6:20 ` [PATCH v4 0/2] tty: serial: dz: convert atomic_* to refcount_* Deepak R Varma
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