From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 74026C982E1 for ; Mon, 21 Sep 2026 07:21:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:References: Subject:From:To:Cc:Message-Id:Date:Content-Type:Content-Transfer-Encoding: Mime-Version:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=nxoDYhmIzh2JJPIArEyFT+HN+oVRry6II7QzeYp2Ns8=; b=uQ1POSKTnkOm8mKU2m8dcIwacg B7M2zJAWJ3tve79OCHZBSn24zRg7bw/T4sPvuITl8H7hC/s3JWhVyFIHQ/QLR9v7KTBlo4sJVyqgJ znZGw9IAGNqlJ9tZqqVzxtFTSPKC66kruMd2eRVw9q0WpnoFawzJ5catec9Vaxbcmv1a6zDioAlfX axcEgdN8N7BW5g+ZzxvpJ+XYA0zOd1XHV9zeE0IiZaDGLMEw7oUV8YL+77oopOwihnlkjZFi/PHOE ZARpE1P0njAkKDvb/C9d2rRZ+DdfcWy2a5pC4wQdx1kdrGtV8hzunFKdavLVvgArVsCq6DVZ2hrPE BR2PgYFg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x8YL8-00000001BZi-1Qrc; Mon, 21 Sep 2026 07:21:26 +0000 Received: from smtpout-03.galae.net ([185.246.85.4]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x8YL5-00000001BYN-3S66 for linux-arm-kernel@lists.infradead.org; Mon, 21 Sep 2026 07:21:25 +0000 Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-03.galae.net (Postfix) with ESMTPS id B66124E40CA3; Mon, 21 Sep 2026 07:21:20 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 76DA460339; Mon, 21 Sep 2026 07:21:20 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 4D6C61032800A; Mon, 21 Sep 2026 09:21:05 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1789975277; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=nxoDYhmIzh2JJPIArEyFT+HN+oVRry6II7QzeYp2Ns8=; b=zHnAy6YhRwPKGEf0y9dvmZY6PdyuCehyShuLCcQ9hRcoCEFxRx6BMqRv8J/NByWFUTsOPO UybaskuxoT1S6hcjn+xsLjoN+6jng6MfTBuO5xYPusGsKOsfcltFGCd8hmOVwuvALGc3V0 xftL6l0nCepix/p2nb+MZHpik/f1U2Kye8vARp3Pa/djqdjtwJ/dnZYQp+XUYAB55Rof0s Ut/KyIf5rzHYGLrPdtLZmUmGXlE5329asARgMt2Hd1t7zwpB58v1iuHV0FQfDsYazTgD2Y Hn9NI9L8z87aSohbMMp24WzHI1zro2CeqOZxWYuGQqFE/Fhxvj5KmIfS67tOsw== Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 21 Sep 2026 09:21:04 +0200 Message-Id: Cc: , , , , , , , "Sashiko" To: "Luca Ceresoli" , "Cristian Ciocaltea" , "Maarten Lankhorst" , "Maxime Ripard" , "Thomas Zimmermann" , "David Airlie" , "Simona Vetter" , "Dave Stevenson" , "Dmitry Baryshkov" , "Andrzej Hajda" , "Neil Armstrong" , "Robert Foss" , "Laurent Pinchart" , "Jonas Karlman" , "Jernej Skrabec" , "Chen-Yu Tsai" , "Samuel Holland" , =?utf-8?q?Ma=C3=ADra_Canal?= , "Raspberry Pi Kernel Maintenance" , "Raphael Gallais-Pou" , "Sandy Huang" , =?utf-8?q?Heiko_St=C3=BCbner?= , "Andy Yan" , "Algea Cao" , "Daniel Stone" , "Liu Ying" , "Phong LE" , "Helge Deller" From: "Luca Ceresoli" Subject: Re: [PATCH v11 12/74] drm/bridge: Fix unlocked list_del in drm_bridge_add() X-Mailer: aerc 0.22.0 References: <20260901-dw-hdmi-qp-scramb-v11-0-bc12954a0688@collabora.com> <20260901-dw-hdmi-qp-scramb-v11-12-bc12954a0688@collabora.com> In-Reply-To: X-Last-TLS-Session-Version: TLSv1.3 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260921_002123_995807_F53485EC X-CRM114-Status: UNSURE ( 9.39 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon Sep 21, 2026 at 9:16 AM CEST, Luca Ceresoli wrote: > Hello Cristian, > > On Tue Sep 1, 2026 at 8:50 PM CEST, Cristian Ciocaltea wrote: >> When re-adding a bridge that was previously removed, drm_bridge_add() >> drops it from bridge_lingering_list without holding bridge_lock. >> >> Both bridge_list and bridge_lingering_list are protected by bridge_lock, >> as they are concurrently modified by drm_bridge_remove() and >> __drm_bridge_free(), and walked by the debugfs 'bridges' file. Running >> the list_empty() test and the list_del_init() outside of the lock may >> therefore corrupt either list. > > The analysis appears correct, with a small nit: __drm_bridge_free() canno= t > touch the list concurrently to other functions, because it only runs when > the refcount is 0, and all other functions tounch the lists only when the= y > have a reference. (Should this sentence be wrong, that would be a big bug= !) Ah, no, I just realized my concern does not stand. Indeed __drm_bridge_free() can run concurrently on a different bridge than the one being handled by other functions, ending up in modifying the same list. So your comment is fully correct: Reviewed-by: Luca Ceresoli Apologies for the noise. Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com