From nobody Sun Apr 12 13:54:19 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1E9CC4332F for ; Sat, 24 Dec 2022 16:56:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231364AbiLXQ4S (ORCPT ); Sat, 24 Dec 2022 11:56:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54058 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229688AbiLXQ4O (ORCPT ); Sat, 24 Dec 2022 11:56:14 -0500 Received: from msg-2.mailo.com (msg-2.mailo.com [213.182.54.12]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EBB162603; Sat, 24 Dec 2022 08:56:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=mailo.com; s=mailo; t=1671900963; bh=3C2JvUsacwZN7GumK7kKdnt5r4dLheWUSYF11PIXW9w=; h=X-EA-Auth:Date:From:To:Cc:Subject:Message-ID:MIME-Version: Content-Type; b=ggGjINSnf2Q/CriYnLlA/iPprvlC6WjH6Wt/FkK99/Y53G0FSxw1/ibA1aLHKTgsK UVPBKZBrXwXm/Nqau3eQH3CsD3Sn/QwvcsuAflG7swohkGXlsjCb5RPTb/iHqPyGiZ ZbhktDeh1d5ewav53hvbBeJKS+ZVgbvtxTpigp8A= Received: by b-2.in.mailobj.net [192.168.90.12] with ESMTP via ip-206.mailobj.net [213.182.55.206] Sat, 24 Dec 2022 17:56:03 +0100 (CET) X-EA-Auth: qanuojNqbxHKKlnmMrAkT89JArbMTly1Cg0TwjOlfKTX30ZqVjzUJ5YwEXDmBZyh+UamKiTd8vbOEEPYgb3JrzVBoS3zH88g Date: Sat, 24 Dec 2022 22:25:58 +0530 From: Deepak R Varma To: "Maciej W. Rozycki" , Greg Kroah-Hartman , Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Saurabh Singh Sengar , Praveen Kumar , Deepak R Varma Subject: [PATCH v2] tty: serial: zs: convert atomic_* to refcount_* APIs for irq_guard Message-ID: MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 --- Changes in v2: 1. Separate the combined change into one variable per patch as suggested by gregkh@linuxfoundation.org 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 t= hat feedback is not applied in this version. Please Note: The patch is compile tested using dec_station.defconfig for MIPS archite= cture. 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 =3D to_zport(uport); struct zs_scc *scc =3D zport->scc; unsigned long flags; - int irq_guard; int ret; - irq_guard =3D atomic_add_return(1, &scc->irq_guard); - if (irq_guard =3D=3D 1) { + refcount_inc(&scc->irq_guard); + if (refcount_read(&scc->irq_guard) =3D=3D 1) { ret =3D request_irq(zport->port.irq, zs_interrupt, IRQF_SHARED, "scc", scc); if (ret) { - atomic_add(-1, &scc->irq_guard); - printk(KERN_ERR "zs: can't get irq %d\n", - zport->port.irq); + refcount_dec(&scc->irq_guard); + printk(KERN_ERR "zs: can't get irq %d\n", zport->port.irq); return ret; } } @@ -806,7 +804,6 @@ static void zs_shutdown(struct uart_port *uport) struct zs_port *zport =3D to_zport(uport); struct zs_scc *scc =3D zport->scc; unsigned long flags; - int irq_guard; spin_lock_irqsave(&scc->zlock, flags); @@ -816,8 +813,7 @@ static void zs_shutdown(struct uart_port *uport) spin_unlock_irqrestore(&scc->zlock, flags); - irq_guard =3D atomic_add_return(-1, &scc->irq_guard); - if (!irq_guard) + if (refcount_dec_and_test(&scc->irq_guard)) free_irq(zport->port.irq, scc); } diff --git a/drivers/tty/serial/zs.h b/drivers/tty/serial/zs.h index 26ef8eafa1c1..bd97b73d7e16 100644 --- a/drivers/tty/serial/zs.h +++ b/drivers/tty/serial/zs.h @@ -40,7 +40,7 @@ struct zs_port { struct zs_scc { struct zs_port zport[2]; spinlock_t zlock; - atomic_t irq_guard; + refcount_t irq_guard; int initialised; }; -- 2.34.1