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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F258C433DF for ; Tue, 4 Aug 2020 01:09:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A5992076C for ; Tue, 4 Aug 2020 01:09:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726615AbgHDBJ1 (ORCPT ); Mon, 3 Aug 2020 21:09:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726276AbgHDBJ1 (ORCPT ); Mon, 3 Aug 2020 21:09:27 -0400 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 37E2AC06174A; Mon, 3 Aug 2020 18:09:27 -0700 (PDT) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1k2lS5-008ndS-Kd; Tue, 04 Aug 2020 01:09:13 +0000 Date: Tue, 4 Aug 2020 02:09:13 +0100 From: Al Viro To: Suren Baghdasaryan Cc: Matthew Wilcox , Kalesh Singh , Jonathan Corbet , Sumit Semwal , Steven Rostedt , Ingo Molnar , linux-doc@vger.kernel.org, LKML , linux-media@vger.kernel.org, DRI mailing list , linaro-mm-sig@lists.linaro.org, linux-fsdevel@vger.kernel.org, Hridya Valsaraju , Ioannis Ilkos , John Stultz , kernel-team Subject: Re: [PATCH 2/2] dmabuf/tracing: Add dma-buf trace events Message-ID: <20200804010913.GA2096725@ZenIV.linux.org.uk> References: <20200803144719.3184138-1-kaleshsingh@google.com> <20200803144719.3184138-3-kaleshsingh@google.com> <20200803154125.GA23808@casper.infradead.org> <20200803161230.GB23808@casper.infradead.org> <20200803222831.GI1236603@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200803222831.GI1236603@ZenIV.linux.org.uk> Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Mon, Aug 03, 2020 at 11:28:31PM +0100, Al Viro wrote: > IOW, what the hell is that horror for? You do realize, for example, that there's > such thing as dup(), right? And dup2() as well. And while we are at it, how > do you keep track of removals, considering the fact that you can stick a file > reference into SCM_RIGHTS datagram sent to yourself, close descriptors and an hour > later pick that datagram, suddenly getting descriptor back? > > Besides, "I have no descriptors left" != "I can't be currently sitting in the middle > of syscall on that sucker"; close() does *NOT* terminate ongoing operations. > > You are looking at the drastically wrong abstraction level. Please, describe what > it is that you are trying to achieve. _IF_ it's "who keeps a particularly long-lived sucker pinned", I would suggest fuser(1) run when you detect that kind of long-lived dmabuf. With events generated by their constructors and destructors, and detection of longevity done based on that. But that's only a semi-blind guess at the things you are trying to achieve; please, describe what it really is.