From nobody Wed Sep 17 01:24:37 2025 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 3D07FC4332F for ; Sat, 24 Dec 2022 08:17:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230334AbiLXIRd (ORCPT ); Sat, 24 Dec 2022 03:17:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229650AbiLXIR3 (ORCPT ); Sat, 24 Dec 2022 03:17:29 -0500 Received: from msg-1.mailo.com (msg-1.mailo.com [213.182.54.11]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99A48DFA2; Sat, 24 Dec 2022 00:17:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=mailo.com; s=mailo; t=1671869837; bh=zGGbbuCFDi0fJZzEl65qs35uUNliyt5H98E+AQuRzag=; h=X-EA-Auth:Date:From:To:Cc:Subject:Message-ID:MIME-Version: Content-Type; b=DP/vkiJcSd3PEEg4xqskXiTahRViQ5P31ekegAAxCjs8dmmtAFWZcgKt/Wglp7Zlp QeS+N88LUL1FHh9X3D7sGKeoGWTstOR5P1yCvZxtyotnkEX9eA3C3kCx7kTnrKOekI lOGgWSwuAjkmkMIzZysPmMhON7k56VI0wbg2i8No= Received: by b-1.in.mailobj.net [192.168.90.11] with ESMTP via ip-206.mailobj.net [213.182.55.206] Sat, 24 Dec 2022 09:17:17 +0100 (CET) X-EA-Auth: AEXDKs6VnpWAu5Q/NjyGfE/fHcrNKz18IDs33rsfJowVHSNknlD1UBEkvSnQchuJuGLbhSZu2gpwXZOXrGnOapzGsmtiYOie Date: Sat, 24 Dec 2022 13:47:12 +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: dz: 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/dz.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-) diff --git a/drivers/tty/serial/dz.c b/drivers/tty/serial/dz.c index b70edc248f8b..0aa59a9beeb7 100644 --- a/drivers/tty/serial/dz.c +++ b/drivers/tty/serial/dz.c @@ -46,7 +46,6 @@ #include #include -#include #include #include #include @@ -77,7 +76,7 @@ struct dz_port { struct dz_mux { struct dz_port dport[DZ_NB_PORT]; refcount_t map_guard; - atomic_t irq_guard; + refcount_t irq_guard; int initialised; }; @@ -400,18 +399,16 @@ static int dz_startup(struct uart_port *uport) struct dz_port *dport =3D to_dport(uport); struct dz_mux *mux =3D dport->mux; unsigned long flags; - int irq_guard; int ret; u16 tmp; - irq_guard =3D atomic_add_return(1, &mux->irq_guard); - if (irq_guard !=3D 1) + refcount_inc(&mux->irq_guard); + if (refcount_read(&mux->irq_guard) !=3D 1) return 0; - ret =3D request_irq(dport->port.irq, dz_interrupt, - IRQF_SHARED, "dz", mux); + ret =3D request_irq(dport->port.irq, dz_interrupt, IRQF_SHARED, "dz", mux= ); if (ret) { - atomic_add(-1, &mux->irq_guard); + refcount_dec(&mux->irq_guard); printk(KERN_ERR "dz: Cannot get IRQ %d!\n", dport->port.irq); return ret; } @@ -441,15 +438,13 @@ static void dz_shutdown(struct uart_port *uport) struct dz_port *dport =3D to_dport(uport); struct dz_mux *mux =3D dport->mux; unsigned long flags; - int irq_guard; u16 tmp; spin_lock_irqsave(&dport->port.lock, flags); dz_stop_tx(&dport->port); spin_unlock_irqrestore(&dport->port.lock, flags); - irq_guard =3D atomic_add_return(-1, &mux->irq_guard); - if (!irq_guard) { + if (refcount_dec_and_test(&mux->irq_guard)) { /* Disable interrupts. */ tmp =3D dz_in(dport, DZ_CSR); tmp &=3D ~(DZ_RIE | DZ_TIE); -- 2.34.1