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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 55AF6C2B9F7 for ; Mon, 24 May 2021 12:58:27 +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 1E18661360 for ; Mon, 24 May 2021 12:58:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1E18661360 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com 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 EF7D9897F0; Mon, 24 May 2021 12:58:24 +0000 (UTC) Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by gabe.freedesktop.org (Postfix) with ESMTPS id 0441D897F0; Mon, 24 May 2021 12:58:17 +0000 (UTC) IronPort-SDR: 1wzONWBGQMdGFSXHUHBQYYRqMQ1YG/2CzMAIUAIPMXfIk9xaZngyghF1jsuADSe7D4lTxOEA/G oVQZi+pcGgvA== X-IronPort-AV: E=McAfee;i="6200,9189,9993"; a="200023926" X-IronPort-AV: E=Sophos;i="5.82,319,1613462400"; d="scan'208";a="200023926" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 May 2021 05:58:17 -0700 IronPort-SDR: Ogq+4QaSK8KwuFo87bEPnZV+uUbHrCiClxYubLN8h59dPR/o4KhRH17TeL/jFxl8lEay/ePbB4 OENP7caSjr6Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.82,319,1613462400"; d="scan'208";a="396938632" Received: from irvmail001.ir.intel.com ([10.43.11.63]) by orsmga006.jf.intel.com with ESMTP; 24 May 2021 05:58:14 -0700 Received: from [10.249.134.123] (mwajdecz-MOBL.ger.corp.intel.com [10.249.134.123]) by irvmail001.ir.intel.com (8.14.3/8.13.6/MailSET/Hub) with ESMTP id 14OCwCEm008734; Mon, 24 May 2021 13:58:13 +0100 Subject: Re: [RFC PATCH 37/97] drm/i915/guc: Add stall timer to non blocking CTB send function To: Matthew Brost , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org References: <20210506191451.77768-1-matthew.brost@intel.com> <20210506191451.77768-38-matthew.brost@intel.com> From: Michal Wajdeczko Message-ID: <7e7ca64d-e5d7-7fd8-b446-7167341c0c92@intel.com> Date: Mon, 24 May 2021 14:58:12 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <20210506191451.77768-38-matthew.brost@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: tvrtko.ursulin@intel.com, jason.ekstrand@intel.com, daniele.ceraolospurio@intel.com, jon.bloomfield@intel.com, daniel.vetter@intel.com, john.c.harrison@intel.com Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 06.05.2021 21:13, Matthew Brost wrote: > Implement a stall timer which fails H2G CTBs once a period of time > with no forward progress is reached to prevent deadlock. > > Also update to ct_write to return -EDEADLK rather than -EPIPE on a > corrupted descriptor. broken descriptor is really separate issue compared to no progress from GuC side, I would really like to keep old error code note that broken CTB descriptor is unrecoverable error, while on other hand, in theory, we could recover from temporary non-moving CTB > > Signed-off-by: John Harrison > Signed-off-by: Daniele Ceraolo Spurio > Signed-off-by: Matthew Brost > --- > drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 48 +++++++++++++++++++++-- > 1 file changed, 45 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c > index af7314d45a78..4eab319d61be 100644 > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c > @@ -69,6 +69,8 @@ static inline struct drm_device *ct_to_drm(struct intel_guc_ct *ct) > #define CTB_H2G_BUFFER_SIZE (SZ_4K) > #define CTB_G2H_BUFFER_SIZE (SZ_4K) > > +#define MAX_US_STALL_CTB 1000000 nit: maybe we should make it a CONFIG value ? > + > struct ct_request { > struct list_head link; > u32 fence; > @@ -315,6 +317,7 @@ int intel_guc_ct_enable(struct intel_guc_ct *ct) > > ct->requests.last_fence = 1; > ct->enabled = true; > + ct->stall_time = KTIME_MAX; > > return 0; > > @@ -378,7 +381,7 @@ static int ct_write(struct intel_guc_ct *ct, > unsigned int i; > > if (unlikely(ctb->broken)) > - return -EPIPE; > + return -EDEADLK; > > if (unlikely(desc->status)) > goto corrupted; > @@ -449,7 +452,7 @@ static int ct_write(struct intel_guc_ct *ct, > CT_ERROR(ct, "Corrupted descriptor head=%u tail=%u status=%#x\n", > desc->head, desc->tail, desc->status); > ctb->broken = true; > - return -EPIPE; > + return -EDEADLK; > } > > /** > @@ -494,6 +497,17 @@ static int wait_for_ct_request_update(struct ct_request *req, u32 *status) > return err; > } > > +static inline bool ct_deadlocked(struct intel_guc_ct *ct) > +{ > + bool ret = ktime_us_delta(ktime_get(), ct->stall_time) > > + MAX_US_STALL_CTB; > + > + if (unlikely(ret)) > + CT_ERROR(ct, "CT deadlocked\n"); > + > + return ret; > +} > + > static inline bool ctb_has_room(struct intel_guc_ct_buffer *ctb, u32 len_dw) > { > struct guc_ct_buffer_desc *desc = ctb->desc; > @@ -505,6 +519,26 @@ static inline bool ctb_has_room(struct intel_guc_ct_buffer *ctb, u32 len_dw) > return space >= len_dw; > } > > +static int has_room_nb(struct intel_guc_ct *ct, u32 len_dw) > +{ > + struct intel_guc_ct_buffer *ctb = &ct->ctbs.send; > + > + lockdep_assert_held(&ct->ctbs.send.lock); > + > + if (unlikely(!ctb_has_room(ctb, len_dw))) { > + if (ct->stall_time == KTIME_MAX) > + ct->stall_time = ktime_get(); > + > + if (unlikely(ct_deadlocked(ct))) > + return -EDEADLK; > + else > + return -EBUSY; > + } > + > + ct->stall_time = KTIME_MAX; > + return 0; > +} > + > static int ct_send_nb(struct intel_guc_ct *ct, > const u32 *action, > u32 len, > @@ -517,7 +551,7 @@ static int ct_send_nb(struct intel_guc_ct *ct, > > spin_lock_irqsave(&ctb->lock, spin_flags); > > - ret = ctb_has_room(ctb, len + 1); > + ret = has_room_nb(ct, len + 1); > if (unlikely(ret)) > goto out; > > @@ -561,11 +595,19 @@ static int ct_send(struct intel_guc_ct *ct, > retry: > spin_lock_irqsave(&ct->ctbs.send.lock, flags); > if (unlikely(!ctb_has_room(ctb, len + 1))) { > + if (ct->stall_time == KTIME_MAX) > + ct->stall_time = ktime_get(); > spin_unlock_irqrestore(&ct->ctbs.send.lock, flags); > + > + if (unlikely(ct_deadlocked(ct))) > + return -EDEADLK; > + likely, instead of duplicating code, you can reuse has_room_nb here > cond_resched(); > goto retry; > } > > + ct->stall_time = KTIME_MAX; > + > fence = ct_get_next_fence(ct); > request.fence = fence; > request.status = 0; >