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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 9BA88C2BA19 for ; Tue, 14 Apr 2020 14:43:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 81A5B2076B for ; Tue, 14 Apr 2020 14:43:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403970AbgDNOnZ (ORCPT ); Tue, 14 Apr 2020 10:43:25 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:42749 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2403941AbgDNOnQ (ORCPT ); Tue, 14 Apr 2020 10:43:16 -0400 Received: by mail-pg1-f194.google.com with SMTP id g6so6081794pgs.9; Tue, 14 Apr 2020 07:43:15 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=ISpaCA7mjN5YjkHYISL3HSq+S++mjTHZ6Lu/DzWzgxg=; b=TIBdpUNc4hD0uk2v2NBi0PeszdnyJON+rnJHdFQYgr7JrMXnHxSIUDHPJEsI5+bkvp R9xbA1No7G+7LpEFf09bDylFQEBEXryTs3dLX4zC7cF2sU0K3pJr1Z6IONZj0F0zj117 eyDvkJrc5O/1oH+nYUdEPJ2WFI2TISRfMhJIdPxWqUOlXgDNOUN7iMIMCU80XS34dWAO NcscPxY+EDhcCEt5EXB9W2PbEN4d+2kH6edPtktidRl+Uf9QHEDt8qEe1Md0wbxj/TLm Leekl/OsI3ILhn5e5R2agXIL0mThBAy6AAsQ6RsgBHCa+rddZnHeizT906kmgMI603Dm KqzA== X-Gm-Message-State: AGi0PubPgpMjmatSIfg87sg+HzWp/Rx5hN2+JFPjeq+KFymRZ4FZE4fc zVw1McGY9DFuzhJo2odXV7Y= X-Google-Smtp-Source: APiQypKYnkcJwA8lBILHDaTEYsu7MMvchjuIIOFNWKTQsueYRWsxR236WZye6IlT0+1XV9h4RXp4Tg== X-Received: by 2002:a63:ec44:: with SMTP id r4mr21490047pgj.425.1586875395070; Tue, 14 Apr 2020 07:43:15 -0700 (PDT) Received: from sultan-box.localdomain (static-198-54-129-52.cust.tzulo.com. [198.54.129.52]) by smtp.gmail.com with ESMTPSA id y123sm11056229pfb.13.2020.04.14.07.43.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2020 07:43:14 -0700 (PDT) Date: Tue, 14 Apr 2020 07:43:09 -0700 From: Sultan Alsawaf To: Chris Wilson Cc: stable@vger.kernel.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter , Matthew Auld , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] drm/i915: Synchronize active and retire callbacks Message-ID: <20200414144309.GB2082@sultan-box.localdomain> References: <20200404024156.GA10382@sultan-box.localdomain> <20200407064007.7599-1-sultan@kerneltoast.com> <20200414061312.GA90768@sultan-box.localdomain> <158685263618.16269.9317893477736764675@build.alporthouse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158685263618.16269.9317893477736764675@build.alporthouse.com> Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Apr 14, 2020 at 09:23:56AM +0100, Chris Wilson wrote: > Quoting Sultan Alsawaf (2020-04-14 07:13:12) > > Chris, > > > > Could you please take a look at this? This really is quite an important fix. > > It's crazy. See a266bf420060 for a patch that should be applied to v5.4 > -Chris What? a266bf420060 was part of 5.4.0-rc7, so it's already in 5.4. And if you read the commit message, you would see that the problem in question affects Linus' tree. You can break i915 in 5.6 by just adding a small delay: diff --git a/drivers/gpu/drm/i915/gt/intel_ring.c b/drivers/gpu/drm/i915/gt/intel_ring.c index 6ff803f397c4..3a7968effdfd 100644 --- a/drivers/gpu/drm/i915/gt/intel_ring.c +++ b/drivers/gpu/drm/i915/gt/intel_ring.c @@ -10,6 +10,7 @@ #include "intel_engine.h" #include "intel_ring.h" #include "intel_timeline.h" +#include unsigned int intel_ring_update_space(struct intel_ring *ring) { @@ -92,6 +93,9 @@ void intel_ring_unpin(struct intel_ring *ring) else i915_gem_object_unpin_map(vma->obj); + mdelay(1); + ring->vaddr = NULL; + i915_vma_make_purgeable(vma); i915_vma_unpin(vma); } This is how I reproduced the race in question. I can't even reach the greeter on my laptop with this, because i915 dies before that. Sultan