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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 07B5BC2BA15 for ; Fri, 3 Apr 2020 17:48:09 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C92CC206F6 for ; Fri, 3 Apr 2020 17:48:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C92CC206F6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7046B6EC4E; Fri, 3 Apr 2020 17:48:08 +0000 (UTC) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by gabe.freedesktop.org (Postfix) with ESMTPS id 72EB06EC4E for ; Fri, 3 Apr 2020 17:48:07 +0000 (UTC) IronPort-SDR: pbCpg3sV87LaTZrC7a3Ad7rQVc+H7E9WorKREqYhk8EoO5xXeSCvZ1W7ueTt4OHg6fotgSlyu2 1cFUIdXcikYw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Apr 2020 10:48:07 -0700 IronPort-SDR: aLiTYRDzd2J0QJ1QjSo7tMdNqpK+/zkqZUSBLF8hM1vLwXY0UDhcFt4pLZlGm25l3oFaUV3Exf nhsnBNA1uzYA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,340,1580803200"; d="scan'208";a="450101738" Received: from adixit-mobl.amr.corp.intel.com (HELO adixit-arch.intel.com) ([10.212.170.25]) by fmsmga005.fm.intel.com with ESMTP; 03 Apr 2020 10:48:06 -0700 Date: Fri, 03 Apr 2020 10:45:09 -0700 Message-ID: <87369k5uqi.wl-ashutosh.dixit@intel.com> From: "Dixit, Ashutosh" To: Chris Wilson In-Reply-To: <158593063457.5852.4620122096592068466@build.alporthouse.com> References: <20200403010120.3067-1-ashutosh.dixit@intel.com> <158593063457.5852.4620122096592068466@build.alporthouse.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?ISO-8859-4?Q?Goj=F2?=) APEL/10.8 EasyPG/1.0.0 Emacs/26 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Subject: Re: [Intel-gfx] [PATCH] drm/i915/perf: Do not clear pollin for small user read buffers X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Fri, 03 Apr 2020 09:17:14 -0700, Chris Wilson wrote: > > Quoting Ashutosh Dixit (2020-04-03 02:01:20) > > It is wrong to block the user thread in the next poll when OA data is > > already available which could not fit in the user buffer provided in > > the previous read. In several cases the exact user buffer size is not > > known. Blocking user space in poll can lead to data loss when the > > buffer size used is smaller than the available data. > > > > This change fixes this issue and allows user space to read all OA data > > even when using a buffer size smaller than the available data using > > multiple non-blocking reads rather than staying blocked in poll till > > the next timer interrupt. > > > > v2: Fix ret value for blocking reads (Umesh) > > v3: Mistake during patch send (Ashutosh) > > v4: Remove -EAGAIN from comment (Umesh) > > v5: Improve condition for clearing pollin and return (Lionel) > > v6: Improve blocking read loop and other cleanups (Lionel) > > v7: Added Cc stable > > > > Cc: Umesh Nerlige Ramappa > > Cc: > > Reviewed-by: Lionel Landwerlin > > Signed-off-by: Ashutosh Dixit > > Did you manage to devise a test case? It is nice (some might say > important) to pair a patch for stable with its regression test. Yes there is a test case here: https://patchwork.freedesktop.org/series/75100/#rev3 Lionel verified that it is fails on stable kernels here: https://patchwork.freedesktop.org/patch/358873/?series=75100&rev=1 Thanks! -- Ashutosh _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx