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=-19.0 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,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 78663C4338F for ; Mon, 16 Aug 2021 13:49:42 +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 323E7632CF for ; Mon, 16 Aug 2021 13:49:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 323E7632CF 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=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 2793C89ED6; Mon, 16 Aug 2021 13:49:36 +0000 (UTC) Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by gabe.freedesktop.org (Postfix) with ESMTPS id 4A53289939; Mon, 16 Aug 2021 13:49:34 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10077"; a="215863460" X-IronPort-AV: E=Sophos;i="5.84,326,1620716400"; d="scan'208";a="215863460" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Aug 2021 06:49:33 -0700 X-IronPort-AV: E=Sophos;i="5.84,326,1620716400"; d="scan'208";a="519661653" Received: from yifeiren-mobl.ccr.corp.intel.com (HELO [10.249.254.101]) ([10.249.254.101]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Aug 2021 06:49:31 -0700 To: Maarten Lankhorst , Matthew Auld Cc: Intel Graphics Development , ML dri-devel References: <20210816084855.75586-1-thomas.hellstrom@linux.intel.com> <00736b43-8abf-ff15-e9dd-5ed54da77379@linux.intel.com> From: =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= Message-ID: <85d1661e-d9bb-f64a-70d5-ffe98e2acf12@linux.intel.com> Date: Mon, 16 Aug 2021 15:49:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <00736b43-8abf-ff15-e9dd-5ed54da77379@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Subject: Re: [Intel-gfx] [PATCH] drm/i915: Ditch the i915_gem_ww_ctx loop member 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: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 8/16/21 3:34 PM, Maarten Lankhorst wrote: > Op 16-08-2021 om 15:30 schreef Thomas Hellström: >> On 8/16/21 3:25 PM, Matthew Auld wrote: >>> On Mon, 16 Aug 2021 at 09:49, Thomas Hellström >>> wrote: >>>> It's only used by the for_i915_gem_ww() macro and we can use >>>> the (typically) on-stack _err variable in its place. >>>> >>>> While initially setting the _err variable to -EDEADLK to enter the >>>> loop, we clear it before actually entering using fetch_and_zero() to >>>> avoid empty loops or code not setting the _err variable running forever. >>>> >>>> Suggested-by: Maarten Lankhorst >>>> Signed-off-by: Thomas Hellström >>>> --- >>>>   drivers/gpu/drm/i915/i915_gem_ww.h | 23 ++++++++--------------- >>>>   1 file changed, 8 insertions(+), 15 deletions(-) >>>> >>>> diff --git a/drivers/gpu/drm/i915/i915_gem_ww.h b/drivers/gpu/drm/i915/i915_gem_ww.h >>>> index f6b1a796667b..98348b1e6182 100644 >>>> --- a/drivers/gpu/drm/i915/i915_gem_ww.h >>>> +++ b/drivers/gpu/drm/i915/i915_gem_ww.h >>>> @@ -7,12 +7,13 @@ >>>> >>>>   #include >>>> >>>> +#include "i915_utils.h" >>>> + >>>>   struct i915_gem_ww_ctx { >>>>          struct ww_acquire_ctx ctx; >>>>          struct list_head obj_list; >>>>          struct drm_i915_gem_object *contended; >>>> -       unsigned short intr; >>>> -       unsigned short loop; >>>> +       bool intr; >>>>   }; >>>> >>>>   void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr); >>>> @@ -23,28 +24,20 @@ void i915_gem_ww_unlock_single(struct drm_i915_gem_object *obj); >>>>   /* Internal functions used by the inlines! Don't use. */ >>>>   static inline int __i915_gem_ww_fini(struct i915_gem_ww_ctx *ww, int err) >>>>   { >>>> -       ww->loop = 0; >>>>          if (err == -EDEADLK) { >>>>                  err = i915_gem_ww_ctx_backoff(ww); >>>>                  if (!err) >>>> -                       ww->loop = 1; >>>> +                       err = -EDEADLK; >>>>          } >>>> >>>> -       if (!ww->loop) >>>> +       if (err != -EDEADLK) >>>>                  i915_gem_ww_ctx_fini(ww); >>>> >>>>          return err; >>>>   } >>>> >>>> -static inline void >>>> -__i915_gem_ww_init(struct i915_gem_ww_ctx *ww, bool intr) >>>> -{ >>>> -       i915_gem_ww_ctx_init(ww, intr); >>>> -       ww->loop = 1; >>>> -} >>>> - >>>> -#define for_i915_gem_ww(_ww, _err, _intr)                      \ >>>> -       for (__i915_gem_ww_init(_ww, _intr); (_ww)->loop;       \ >>>> +#define for_i915_gem_ww(_ww, _err, _intr)                        \ >>>> +       for (i915_gem_ww_ctx_init(_ww, _intr), (_err) = -EDEADLK; \ >>>> +            fetch_and_zero(&_err) == -EDEADLK;                   \ >>> Doesn't this now hide "normal" errors, like say get_pages() returning >>> -ENOSPC or so? >> Yes, good catch. We should either just clear the -EDEADLK case, or not clear the error at all.. >> >> /Thomas > I believe not setting _err is a bug anyway. Why would you do such a loop without at least one err = ww_mutex_lock(&ww); ? > > Infinite loop would catch that at first test. OK, I'll skip the clearing then. /Thomas > > ~Maarten >