From patchwork Mon Sep 21 16:27:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "gregkh@linuxfoundation.org" X-Patchwork-Id: 309420 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=-14.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT 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 E0D1BC43468 for ; Mon, 21 Sep 2020 16:46:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE80523888 for ; Mon, 21 Sep 2020 16:46:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600706791; bh=7O5/mVTf6EMICu1ADEXtjWEh7thCk7vf25nVfFHLSU4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=q+GFntL+0XIbp5NMGzQ6is8hilzLRjrEu/OwLoKfPONsgDodvOgFlPF3G8jInPGVM HtHyoJQYIikEmghUQ7SNzIiA3QFk85o2cuIi3iABJUEB6hRgV73Ms3DRcvOjI8hgJ2 7pbWjlZlI67XNsw80iYYpoJQeuhu8Q2qsFKbhHDs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729261AbgIUQqa (ORCPT ); Mon, 21 Sep 2020 12:46:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:52632 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727824AbgIUQq0 (ORCPT ); Mon, 21 Sep 2020 12:46:26 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D04BE23888; Mon, 21 Sep 2020 16:46:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600706785; bh=7O5/mVTf6EMICu1ADEXtjWEh7thCk7vf25nVfFHLSU4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aD6jlBuLBF49rgkArm66Piep2EfPSJlQIT8L/QxW15meOnfLSwOCmUpddDUGZVQNa ZDEdWFSAqQMD8WjGj102t85tIDbNGqAhLiZ8iAsEq6aMPxbRk3sAJz6oZKrVYHZM1A QWGaTBxLgirpOZubZYwQe6beUEJouepvfGHkcD5c= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Chris Wilson , Tvrtko Ursulin , Rodrigo Vivi , Joonas Lahtinen , Jani Nikula , Sasha Levin Subject: [PATCH 5.8 064/118] drm/i915/gem: Reduce context termination list iteration guard to RCU Date: Mon, 21 Sep 2020 18:27:56 +0200 Message-Id: <20200921162039.326069868@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200921162036.324813383@linuxfoundation.org> References: <20200921162036.324813383@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Chris Wilson [ Upstream commit c2314b8bd4c009793b6f9d57bc8363af034e02ca ] As we now protect the timeline list using RCU, we can drop the timeline->mutex for guarding the list iteration during context close, as we are searching for an inflight request. Any new request will see the context is banned and not be submitted. In doing so, pull the checks for a concurrent submission of the request (notably the i915_request_completed()) under the engine spinlock, to fully serialise with __i915_request_submit()). That is in the case of preempt-to-busy where the request may be completed during the __i915_request_submit(), we need to be careful that we sample the request status after serialising so that we don't miss the request the engine is actually submitting. Fixes: 4a3174152147 ("drm/i915/gem: Refine occupancy test in kill_context()") Signed-off-by: Chris Wilson Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20200806105954.7766-1-chris@chris-wilson.co.uk Signed-off-by: Rodrigo Vivi Signed-off-by: Joonas Lahtinen (cherry picked from commit 736e785f9b28cd9ef2d16a80960a04fd00e64b22) Signed-off-by: Jani Nikula Signed-off-by: Sasha Levin --- drivers/gpu/drm/i915/gem/i915_gem_context.c | 32 ++++++++++++--------- 1 file changed, 19 insertions(+), 13 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index 30c229fcb4046..6dce7d8b463eb 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -440,29 +440,36 @@ static bool __cancel_engine(struct intel_engine_cs *engine) return __reset_engine(engine); } -static struct intel_engine_cs *__active_engine(struct i915_request *rq) +static bool +__active_engine(struct i915_request *rq, struct intel_engine_cs **active) { struct intel_engine_cs *engine, *locked; + bool ret = false; /* * Serialise with __i915_request_submit() so that it sees * is-banned?, or we know the request is already inflight. + * + * Note that rq->engine is unstable, and so we double + * check that we have acquired the lock on the final engine. */ locked = READ_ONCE(rq->engine); spin_lock_irq(&locked->active.lock); while (unlikely(locked != (engine = READ_ONCE(rq->engine)))) { spin_unlock(&locked->active.lock); - spin_lock(&engine->active.lock); locked = engine; + spin_lock(&locked->active.lock); } - engine = NULL; - if (i915_request_is_active(rq) && rq->fence.error != -EIO) - engine = rq->engine; + if (!i915_request_completed(rq)) { + if (i915_request_is_active(rq) && rq->fence.error != -EIO) + *active = locked; + ret = true; + } spin_unlock_irq(&locked->active.lock); - return engine; + return ret; } static struct intel_engine_cs *active_engine(struct intel_context *ce) @@ -473,17 +480,16 @@ static struct intel_engine_cs *active_engine(struct intel_context *ce) if (!ce->timeline) return NULL; - mutex_lock(&ce->timeline->mutex); - list_for_each_entry_reverse(rq, &ce->timeline->requests, link) { - if (i915_request_completed(rq)) - break; + rcu_read_lock(); + list_for_each_entry_rcu(rq, &ce->timeline->requests, link) { + if (i915_request_is_active(rq) && i915_request_completed(rq)) + continue; /* Check with the backend if the request is inflight */ - engine = __active_engine(rq); - if (engine) + if (__active_engine(rq, &engine)) break; } - mutex_unlock(&ce->timeline->mutex); + rcu_read_unlock(); return engine; }