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 265CCC33CB2 for ; Wed, 29 Jan 2020 09:30:36 +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 3D4E920716 for ; Wed, 29 Jan 2020 09:30:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D4E920716 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 DA6F36F4BF; Wed, 29 Jan 2020 09:30:34 +0000 (UTC) Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by gabe.freedesktop.org (Postfix) with ESMTPS id 27C586F4BF for ; Wed, 29 Jan 2020 09:30:33 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Jan 2020 01:30:32 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,377,1574150400"; d="scan'208";a="232363403" Received: from gaia.fi.intel.com ([10.237.72.192]) by orsmga006.jf.intel.com with ESMTP; 29 Jan 2020 01:30:31 -0800 Received: by gaia.fi.intel.com (Postfix, from userid 1000) id 9DF465C1DD3; Wed, 29 Jan 2020 11:29:43 +0200 (EET) From: Mika Kuoppala To: Chris Wilson , intel-gfx@lists.freedesktop.org In-Reply-To: <20200128171614.3845825-1-chris@chris-wilson.co.uk> References: <20200128171614.3845825-1-chris@chris-wilson.co.uk> Date: Wed, 29 Jan 2020 11:29:43 +0200 Message-ID: <87k15aa9vc.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: > 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? Even if the top level READ_ONCE would guard the next one, for documentation. -Mika > rcu_read_lock(); /* protect peeking at execlists->active */ > execlists_dequeue(engine); > rcu_read_unlock(); > -- > 2.25.0 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx