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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 15605C433FE for ; Tue, 22 Nov 2022 10:50:47 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E713410E039; Tue, 22 Nov 2022 10:50:45 +0000 (UTC) Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by gabe.freedesktop.org (Postfix) with ESMTPS id AC6C910E039; Tue, 22 Nov 2022 10:50:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1669114243; x=1700650243; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=hTmJOcb2/F7Ns1JLBwhouIBn1IhO1I7OWMGVPOceiuo=; b=VXfi/QW28fc+/PX7fGlCqBww5Po7JrSIxucL+LxvxPe0AU2WWXVM+eSH iZncjyDpVUuKQCAM0KhAbmtrbTZPGSZNhMpQr60IK/UebrM8IYET4FcGu Ztk2cB+09gB2gF0p5706qfSyRtqvsnDXSDBTP1FdnAnR37ta38WvJ/Wom jpUxb+ne/BkEvfVcfc97x7ySVjSVdu16kuQPs1X/IPbGQYAahZrXt5WZ9 YBTc553cw0w6VqujgC+yFrTeVJzn3HgbzjAf/EpdLegjjI5NcWryyUVfm mfbw38PWstppjn/pggqDt0n/KVUcW/OUThIIfyQO8bNjMXA+/J0uyESlN w==; X-IronPort-AV: E=McAfee;i="6500,9779,10538"; a="312489079" X-IronPort-AV: E=Sophos;i="5.96,183,1665471600"; d="scan'208";a="312489079" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Nov 2022 02:50:43 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10538"; a="970428712" X-IronPort-AV: E=Sophos;i="5.96,183,1665471600"; d="scan'208";a="970428712" Received: from camorino-mobl.ger.corp.intel.com (HELO [10.213.209.233]) ([10.213.209.233]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Nov 2022 02:50:40 -0800 Message-ID: <6a465c20-b0a7-4beb-6d1b-4ff66a29975f@linux.intel.com> Date: Tue, 22 Nov 2022 10:50:38 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Content-Language: en-US To: Janusz Krzysztofik , Joonas Lahtinen References: <20221121145655.75141-1-janusz.krzysztofik@linux.intel.com> <20221121145655.75141-3-janusz.krzysztofik@linux.intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc In-Reply-To: <20221121145655.75141-3-janusz.krzysztofik@linux.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Intel-gfx] [PATCH v3 2/2] drm/i915: Never return 0 if not all requests retired 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: Daniel Vetter , intel-gfx@lists.freedesktop.org, Chris Wilson , dri-devel@lists.freedesktop.org, Andrzej Hajda , Nirmoy Das Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 21/11/2022 14:56, Janusz Krzysztofik wrote: > Users of intel_gt_retire_requests_timeout() expect 0 return value on > success. However, we have no protection from passing back 0 potentially > returned by a call to dma_fence_wait_timeout() when it succedes right > after its timeout has expired. Is this talking about a potential weakness, or ambiguous kerneldoc, of dma_fence_wait_timeout, dma_fence_default_wait and i915_request_wait_timeout? They appear to say 0 return means timeout, implying unsignaled fence. In other words signaled must return positive remaining timeout. Implementations seems to allow a race which indeed appears that return 0 and signaled fence is possible. If dma_fence_wait can indeed return 0 even when a request is signaled, then how is timeout ?: -ETIME below correct? It isn't a chance for false negative in its' callers? Regards, Tvrtko > Replace 0 with -ETIME before potentially using the timeout value as return > code, so -ETIME is returned if there are still some requests not retired > after timeout, 0 otherwise. > > v3: Use conditional expression, more compact but also better reflecting > intention standing behind the change. > > v2: Move the added lines down so flush_submission() is not affected. > > Fixes: f33a8a51602c ("drm/i915: Merge wait_for_timelines with retire_request") > Signed-off-by: Janusz Krzysztofik > Reviewed-by: Andrzej Hajda > Cc: stable@vger.kernel.org # v5.5+ > --- > drivers/gpu/drm/i915/gt/intel_gt_requests.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_requests.c b/drivers/gpu/drm/i915/gt/intel_gt_requests.c > index edb881d756309..1dfd01668c79c 100644 > --- a/drivers/gpu/drm/i915/gt/intel_gt_requests.c > +++ b/drivers/gpu/drm/i915/gt/intel_gt_requests.c > @@ -199,7 +199,7 @@ out_active: spin_lock(&timelines->lock); > if (remaining_timeout) > *remaining_timeout = timeout; > > - return active_count ? timeout : 0; > + return active_count ? timeout ?: -ETIME : 0; > } > > static void retire_work_handler(struct work_struct *work)