From patchwork Fri Nov 8 07:18:54 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Hellstrom X-Patchwork-Id: 3158051 Return-Path: X-Original-To: patchwork-dri-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 04321C045B for ; Fri, 8 Nov 2013 14:43:50 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id D02F2201BB for ; Fri, 8 Nov 2013 14:43:48 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) by mail.kernel.org (Postfix) with ESMTP id 69901201B7 for ; Fri, 8 Nov 2013 14:43:47 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 26C4A8768F810; Fri, 8 Nov 2013 06:43:09 -0800 (PST) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from smtp-outbound-1.vmware.com (smtp-outbound-1.vmware.com [208.91.2.12]) by gabe.freedesktop.org (Postfix) with ESMTP id 7385AEDBE6 for ; Thu, 7 Nov 2013 23:19:19 -0800 (PST) Received: from sc9-mailhost3.vmware.com (sc9-mailhost3.vmware.com [10.113.161.73]) by smtp-outbound-1.vmware.com (Postfix) with ESMTP id BDF8B2982D; Thu, 7 Nov 2013 23:19:18 -0800 (PST) Received: from zcs-prod-ext-mta-2.vmware.com (zcs-prod-ext-mta-2.vmware.com [10.113.62.224]) by sc9-mailhost3.vmware.com (Postfix) with ESMTP id BC474403D0; Thu, 7 Nov 2013 23:19:18 -0800 (PST) Received: from zcs-prod-ext-mta-2.vmware.com (localhost.localdomain [127.0.0.1]) by zcs-prod-ext-mta-2.vmware.com (Postfix) with ESMTP id 8DF7BC005D; Thu, 7 Nov 2013 23:19:33 -0800 (PST) Received: from localhost.localdomain (zimbra-prod-ext-proxy-vip.vmware.com [10.113.63.87]) by zcs-prod-ext-mta-2.vmware.com (Postfix) with ESMTPSA; Thu, 7 Nov 2013 23:19:32 -0800 (PST) From: Thomas Hellstrom To: dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org Subject: [PATCH RFC] dma-buf/fs Add get_[file|dma_buf]_unless_doomed Date: Thu, 7 Nov 2013 23:18:54 -0800 Message-Id: <1383895134-4535-1-git-send-email-thellstrom@vmware.com> X-Mailer: git-send-email 1.7.10.4 Cc: Thomas Hellstrom X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: dri-devel-bounces@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In this context, a "doomed" object is an object whose refcount has reached zero, but that has not yet been freed. To avoid mutual refcounting vmwgfx need to have a non-refcounted pointer to a dma-buf in a lookup structure. The pointer is removed in the dma-buf destructor. To allow lookup-structure private locks we need get_dma_buf_unless_doomed(). This common refcounting scenario is described with examples in detail in the kref documentaion. The solution with local locks is under kref_get_unless_zero(). See also kobject_get_unless_zero() and its commit message. Since dma-bufs are using the attached file for refcounting, get_dma_buf_unless_doomed maps directly to a get_file_unless_doomed. Signed-off-by: Thomas Hellstrom --- include/linux/dma-buf.h | 16 ++++++++++++++++ include/linux/fs.h | 15 +++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index dfac5ed..6e58144 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -162,6 +162,22 @@ static inline void get_dma_buf(struct dma_buf *dmabuf) get_file(dmabuf->file); } +/** + * get_dma_buf_unless_doomed - convenience wrapper for get_file_unless_doomed + * + * @dmabuf: [in] pointer to dma_buf + * + * Obtain a dma-buf reference from a lookup structure that doesn't refcount + * the dma-buf, but synchronizes with its release method to make sure it has + * not been freed yet. See for example kref_get_unless_zero documentation. + * Returns true if refcounting succeeds, false otherwise. + */ +static inline bool __must_check +get_dma_buf_unless_doomed(struct dma_buf *dmabuf) +{ + return get_file_unless_doomed(dmabuf->file); +} + struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf, struct device *dev); void dma_buf_detach(struct dma_buf *dmabuf, diff --git a/include/linux/fs.h b/include/linux/fs.h index 3f40547..a96c333 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -824,6 +824,21 @@ static inline struct file *get_file(struct file *f) atomic_long_inc(&f->f_count); return f; } + +/** + * get_file_unless_doomed - convenience wrapper for get_file_unless_doomed + * @file: [in] pointer to file + * + * Obtain a file reference from a lookup structure that doesn't refcount + * the file, but synchronizes with its release method to make sure it has + * not been freed yet. See for example kref_get_unless_zero documentation. + * Returns true if refcounting succeeds, false otherwise. + */ +static inline bool __must_check get_file_unless_doomed(struct file *f) +{ + return atomic_long_inc_not_zero(&f->f_count) != 0L; +} + #define fput_atomic(x) atomic_long_add_unless(&(x)->f_count, -1, 1) #define file_count(x) atomic_long_read(&(x)->f_count)