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=-0.8 required=3.0 tests=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 7D17AC33CB1 for ; Wed, 15 Jan 2020 14:02:13 +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 5CB3124656 for ; Wed, 15 Jan 2020 14:02:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5CB3124656 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B35386EA18; Wed, 15 Jan 2020 14:02:12 +0000 (UTC) Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id E57AD6EA18 for ; Wed, 15 Jan 2020 14:02:10 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from localhost (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP (TLS) id 19889159-1500050 for multiple; Wed, 15 Jan 2020 14:01:22 +0000 MIME-Version: 1.0 To: Sean Paul From: Chris Wilson In-Reply-To: <20200115134158.GC25564@art_vandelay> References: <20200114172155.215463-1-sean@poorly.run> <157908459623.12549.3531242692320169983@skylake-alporthouse-com> <20200115134158.GC25564@art_vandelay> Message-ID: <157909687975.14122.1932646175287417072@skylake-alporthouse-com> User-Agent: alot/0.6 Subject: Re: [PATCH v4] drm/trace: Buffer DRM logs in a ringbuffer accessible via debugfs Date: Wed, 15 Jan 2020 14:01:19 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-doc@vger.kernel.org, David Airlie , Daniel Vetter , Jonathan Corbet , dri-devel@lists.freedesktop.org, Sean Paul , Steven Rostedt , Thomas Zimmermann , Sean Paul Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Quoting Sean Paul (2020-01-15 13:41:58) > On Wed, Jan 15, 2020 at 10:36:36AM +0000, Chris Wilson wrote: > > Quoting Sean Paul (2020-01-14 17:21:43) > > > From: Sean Paul > > > > > > This patch uses a ring_buffer to keep a "flight recorder" (name credit Weston) > > > of DRM logs for a specified set of debug categories. The user writes a > > > bitmask of debug categories to the "trace_mask" node and can read log > > > messages from the "trace" node. > > > > > > These nodes currently exist in debugfs under the dri directory. I > > > intended on exposing all of this through tracefs originally, but the > > > tracefs entry points are not exposed, so there's no way to create > > > tracefs files from drivers at the moment. I think it would be a > > > worthwhile endeavour, but one requiring more time and conversation to > > > ensure the drm traces fit somewhere sensible. > > > > Fwiw, I have a need for client orientated debug message store, with > > the primary purpose of figuring out -EINVAL. We need per-client so we can > > put sensitive information about the potentially buggy client behaviour, > > and of course it needs to be accessible by the non-privileged client. > > > > On the execution side, it's easy to keep track of the client so we could > > trace execution flow per client, within reason. And we could do > > similarly for kms clients. > > Could you build such a thing with drm_trace underpinning it, just put the > pertinent information in the message? Not as is. The global has to go, and there's no use for debugfs. So we are just left with a sprintf() around a ring_buffer. I am left in the same position as just wanting to generalise tracek to take the ringbuffer as a parameter. > > Just chiming to say, I don't think a duplicate of dmesg hidden inside > > debugfs achieves much. But a generic tracek-esque ringbuf would be very > > useful -- even if only so we can separate our GEM_TRACE from the global > > tracek. > > I think that's essentially what we've got, I've just narrowly focused on > surfacing debug logs. If drm_trace_printf were exported, replacing > GEM_TRACE would be as simple as s/trace_printk/drm_trace_printf/. Initially I > thought exporting it to drivers would be a bad idea, but I'm open to changing my > mind on this as long as drivers are using it responsibly. I definitely can't make the mistake of flooding kms tracing with overwhelming execution traces -- we can't go back to mixing kms traces with execution traces. -Chris _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel