From nobody Mon Sep 15 11:53:47 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 147D5C54EBE for ; Thu, 12 Jan 2023 17:37:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231679AbjALRhX (ORCPT ); Thu, 12 Jan 2023 12:37:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55098 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231891AbjALRgZ (ORCPT ); Thu, 12 Jan 2023 12:36:25 -0500 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C756C7826E; Thu, 12 Jan 2023 08:57:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1673542679; x=1705078679; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=gA5/njLr6I387+ufsBDRnAQjKtZ0ST5kVZFmIu51Hl0=; b=OsJ7nj+RG9O+8htK08tYbUjwRBCUde4UInFKJj9eHhZ3/IhKYGzacD6k fEm9/5SW13OlNcVtbSc0qqmoylBSRDCp0+rM5G0GreWqig3F1riso2cJm k8Lepfn9IzWLDi3Lftq28XJS6scZpdtApcjEYtz5g8H5KepFzQCvrhICc Zrej3Rq9Pr93HbrK/O5jeuNeM3XIEF58diEzdPdUIFWNdK4vcj2mX1rFS hHoGlXhZonPDwoBVGHv9WgWfsxTL7jkQXP3PwSH6n49ZwAoO/I0nH7260 6ftB3MZgmyCGhnUU19mn5q4PD4AVQqL+1pgZ6ToOUQDrDlgex34OH2Gbd A==; X-IronPort-AV: E=McAfee;i="6500,9779,10588"; a="325016435" X-IronPort-AV: E=Sophos;i="5.97,211,1669104000"; d="scan'208";a="325016435" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jan 2023 08:56:46 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10588"; a="651232719" X-IronPort-AV: E=Sophos;i="5.97,211,1669104000"; d="scan'208";a="651232719" Received: from jacton-mobl.ger.corp.intel.com (HELO localhost.localdomain) ([10.213.195.171]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jan 2023 08:56:42 -0800 From: Tvrtko Ursulin To: Intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo , Johannes Weiner , Zefan Li , Dave Airlie , Daniel Vetter , Rob Clark , =?UTF-8?q?St=C3=A9phane=20Marchesin?= , "T . J . Mercier" , Kenny.Ho@amd.com, =?UTF-8?q?Christian=20K=C3=B6nig?= , Brian Welty , Tvrtko Ursulin Subject: [RFC 05/12] drm/cgroup: Allow safe external access to file_priv Date: Thu, 12 Jan 2023 16:56:02 +0000 Message-Id: <20230112165609.1083270-6-tvrtko.ursulin@linux.intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230112165609.1083270-1-tvrtko.ursulin@linux.intel.com> References: <20230112165609.1083270-1-tvrtko.ursulin@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Tvrtko Ursulin Entry points from the cgroup subsystem into the drm cgroup controller will need to walk the file_priv structures associated with registered clients and since those are not RCU protected lets add a hack for now to make this safe. Signed-off-by: Tvrtko Ursulin --- drivers/gpu/drm/drm_cgroup.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/gpu/drm/drm_cgroup.c b/drivers/gpu/drm/drm_cgroup.c index d91512a560ff..46b012d2be42 100644 --- a/drivers/gpu/drm/drm_cgroup.c +++ b/drivers/gpu/drm/drm_cgroup.c @@ -18,6 +18,13 @@ __del_clients(struct drm_pid_clients *clients, if (atomic_dec_and_test(&clients->num)) { xa_erase(&drm_pid_clients, pid); kfree_rcu(clients, rcu); + + /* + * FIXME: file_priv is not RCU protected so we add this hack + * to avoid any races with code which walks clients->file_list + * and accesses file_priv. + */ + synchronize_rcu(); } } =20 --=20 2.34.1