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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 C41E2C2D0DB for ; Wed, 29 Jan 2020 13:10:16 +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 A276E205F4 for ; Wed, 29 Jan 2020 13:10:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A276E205F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.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 0BDA289A5D; Wed, 29 Jan 2020 13:10:16 +0000 (UTC) Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by gabe.freedesktop.org (Postfix) with ESMTPS id B4BD789565 for ; Wed, 29 Jan 2020 13:10:14 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Jan 2020 05:10:05 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,378,1574150400"; d="scan'208";a="247052257" Received: from gaia.fi.intel.com ([10.237.72.192]) by orsmga002.jf.intel.com with ESMTP; 29 Jan 2020 05:10:04 -0800 Received: by gaia.fi.intel.com (Postfix, from userid 1000) id 1C7275C1DFA; Wed, 29 Jan 2020 15:09:17 +0200 (EET) From: Mika Kuoppala To: Chris Wilson , intel-gfx@lists.freedesktop.org In-Reply-To: <158029040255.10244.7113266483710281976@skylake-alporthouse-com> References: <20200128171614.3845825-1-chris@chris-wilson.co.uk> <87k15aa9vc.fsf@gaia.fi.intel.com> <158029040255.10244.7113266483710281976@skylake-alporthouse-com> Date: Wed, 29 Jan 2020 15:09:17 +0200 Message-ID: <87h80e9zpe.fsf@gaia.fi.intel.com> MIME-Version: 1.0 Subject: Re: [Intel-gfx] [PATCH] drm/i915/execlist: Mark up racy read of execlists->pending[0] 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Chris Wilson writes: > Quoting Mika Kuoppala (2020-01-29 09:29:43) >> Chris Wilson writes: >> >> > We write to execlists->pending[0] in process_csb() to acknowledge the >> > completion of the ESLP update, outside of the main spinlock. When we >> > check the current status of the previous submission in >> > __execlists_submission_tasklet() we should therefore use READ_ONCE() to >> > reflect and document the unsynchronized read. >> > >> > Signed-off-by: Chris Wilson >> > Cc: Tvrtko Ursulin >> > --- >> > drivers/gpu/drm/i915/gt/intel_lrc.c | 2 +- >> > 1 file changed, 1 insertion(+), 1 deletion(-) >> > >> > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c >> > index cf6c43bd540a..058484958e87 100644 >> > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c >> > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c >> > @@ -2347,7 +2347,7 @@ static void process_csb(struct intel_engine_cs *engine) >> > static void __execlists_submission_tasklet(struct intel_engine_cs *const engine) >> > { >> > lockdep_assert_held(&engine->active.lock); >> > - if (!engine->execlists.pending[0]) { >> > + if (!READ_ONCE(engine->execlists.pending[0])) { >> >> With same token, should we also include assert_pending_invalid() >> read of pending with READ_ONCE? > > That happens on the control paths, so the state of pending[] at that > point should be static (and the compiler can be left to its own > devices). It should be static. Fair enough Reviewed-by: Mika Kuoppala _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx