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=-16.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, 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 88034C4320E for ; Thu, 2 Sep 2021 12:43:00 +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 495D6610CD for ; Thu, 2 Sep 2021 12:43:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 495D6610CD 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 E611F6E51C; Thu, 2 Sep 2021 12:42:56 +0000 (UTC) Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8E4096E51C; Thu, 2 Sep 2021 12:42:55 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10094"; a="215961113" X-IronPort-AV: E=Sophos;i="5.84,372,1620716400"; d="scan'208";a="215961113" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2021 05:42:55 -0700 X-IronPort-AV: E=Sophos;i="5.84,372,1620716400"; d="scan'208";a="461639444" Received: from rlsmith2-mobl1.amr.corp.intel.com (HELO [10.213.229.210]) ([10.213.229.210]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Sep 2021 05:42:52 -0700 Subject: Re: [Intel-gfx] [PATCH 01/11] drm/i915: Release i915_gem_context from a worker To: Daniel Vetter , DRI Development Cc: Intel Graphics Development , Daniel Vetter , Jon Bloomfield , Chris Wilson , Maarten Lankhorst , Joonas Lahtinen , =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= , Matthew Auld , Lionel Landwerlin , Dave Airlie , Jason Ekstrand References: <20210813203033.3179400-1-daniel.vetter@ffwll.ch> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <9d8cba62-e1e1-a62c-1482-89d2db49d5af@linux.intel.com> Date: Thu, 2 Sep 2021 13:42:49 +0100 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: <20210813203033.3179400-1-daniel.vetter@ffwll.ch> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 13/08/2021 21:30, Daniel Vetter wrote: > The only reason for this really is the i915_gem_engines->fence > callback engines_notify(), which exists purely as a fairly funky > reference counting scheme for that. Otherwise all other callers are > from process context, and generally fairly benign locking context. There is reset which definitely isn't process context. Otherwise I did not really get from the commit message is this patch fixing an existing problem or preparing something for the future. If the former then as I wrote above - I am pretty sure there are call sites from the tasklet already. Regards, Tvrtko > Unfortunately untangling that requires some major surgery, and we have > a few i915_gem_context reference counting bugs that need fixing, and > they blow in the current hardirq calling context, so we need a > stop-gap measure. > > Put a FIXME comment in when this should be removable again. > > Signed-off-by: Daniel Vetter > Cc: Jon Bloomfield > Cc: Chris Wilson > Cc: Maarten Lankhorst > Cc: Joonas Lahtinen > Cc: Daniel Vetter > Cc: "Thomas Hellström" > Cc: Matthew Auld > Cc: Lionel Landwerlin > Cc: Dave Airlie > Cc: Jason Ekstrand > --- > drivers/gpu/drm/i915/gem/i915_gem_context.c | 13 +++++++++++-- > drivers/gpu/drm/i915/gem/i915_gem_context_types.h | 12 ++++++++++++ > 2 files changed, 23 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c > index fd169cf2f75a..051bc357ff65 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c > @@ -986,9 +986,10 @@ static struct i915_gem_engines *user_engines(struct i915_gem_context *ctx, > return err; > } > > -void i915_gem_context_release(struct kref *ref) > +static void i915_gem_context_release_work(struct work_struct *work) > { > - struct i915_gem_context *ctx = container_of(ref, typeof(*ctx), ref); > + struct i915_gem_context *ctx = container_of(work, typeof(*ctx), > + release_work); > > trace_i915_context_free(ctx); > GEM_BUG_ON(!i915_gem_context_is_closed(ctx)); > @@ -1002,6 +1003,13 @@ void i915_gem_context_release(struct kref *ref) > kfree_rcu(ctx, rcu); > } > > +void i915_gem_context_release(struct kref *ref) > +{ > + struct i915_gem_context *ctx = container_of(ref, typeof(*ctx), ref); > + > + queue_work(ctx->i915->wq, &ctx->release_work); > +} > + > static inline struct i915_gem_engines * > __context_engines_static(const struct i915_gem_context *ctx) > { > @@ -1303,6 +1311,7 @@ i915_gem_create_context(struct drm_i915_private *i915, > ctx->sched = pc->sched; > mutex_init(&ctx->mutex); > INIT_LIST_HEAD(&ctx->link); > + INIT_WORK(&ctx->release_work, i915_gem_context_release_work); > > spin_lock_init(&ctx->stale.lock); > INIT_LIST_HEAD(&ctx->stale.engines); > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h > index 94c03a97cb77..0c38789bd4a8 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h > @@ -288,6 +288,18 @@ struct i915_gem_context { > */ > struct kref ref; > > + /** > + * @release_work: > + * > + * Work item for deferred cleanup, since i915_gem_context_put() tends to > + * be called from hardirq context. > + * > + * FIXME: The only real reason for this is &i915_gem_engines.fence, all > + * other callers are from process context and need at most some mild > + * shuffling to pull the i915_gem_context_put() call out of a spinlock. > + */ > + struct work_struct release_work; > + > /** > * @rcu: rcu_head for deferred freeing. > */ >