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=-3.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 47AB9C4363A for ; Mon, 26 Oct 2020 19:16:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DB5762085B for ; Mon, 26 Oct 2020 19:16:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=gmx.net header.i=@gmx.net header.b="EnJhxJKQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1783596AbgJZTQG (ORCPT ); Mon, 26 Oct 2020 15:16:06 -0400 Received: from mout.gmx.net ([212.227.15.15]:57401 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1783221AbgJZTQF (ORCPT ); Mon, 26 Oct 2020 15:16:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1603739725; bh=52jZV+hgar8meUv7frV/fyzM7mQ0U5DFY1NWKhPggTQ=; h=X-UI-Sender-Class:Subject:From:To:Cc:Date:In-Reply-To:References; b=EnJhxJKQPuSXh7lixi6X/UKhi/ht13Zg5v/rvuQFKhT56Nszc4mAS1UO7zgxv70WK JVso3d7xEUvaBLwKFml4GbfIOqCRVQM2PGDcrtZheQfmXCoUG3jt9dXm/4F9QVGKKr ta81Gjfohbb+Cn/mQLdzzJaX90+1mbYTx+pMaP1E= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from homer.simpson.net ([185.146.51.69]) by mail.gmx.com (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1M9o1v-1kRNKz2wPl-005s9Y; Mon, 26 Oct 2020 20:15:24 +0100 Message-ID: <431e81699f2310eabfe5af0a3de400ab99d9323b.camel@gmx.de> Subject: Re: kvm+nouveau induced lockdep gripe From: Mike Galbraith To: Sebastian Andrzej Siewior , Hillf Danton Cc: Thomas Gleixner , LKML , linux-rt-users , Steven Rostedt , Ben Skeggs Date: Mon, 26 Oct 2020 20:15:23 +0100 In-Reply-To: <20201026173107.quylcy6fgjvrqat6@linutronix.de> References: <20201021125324.ualpvrxvzyie6d7d@linutronix.de> <20201023090108.5lunh4vqfpkllmap@linutronix.de> <20201024022236.19608-1-hdanton@sina.com> <20201024050000.8104-1-hdanton@sina.com> <20201026173107.quylcy6fgjvrqat6@linutronix.de> Content-Type: text/plain; charset="ISO-8859-15" User-Agent: Evolution 3.34.4 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:h2fpWdnodak2evkUSoMLFaQ15SXdRAny+od2n1CA1xkjjRMcDde 7GApg72QlnT62qxt8dqau5208wtkgEoGeAPjPKNL3jv841rd8yV5HZrVFbFdOeK8k3uqE2l OWrkCTQ5bG02PlV9giTDVEhqzU5QXwUWXBLT1BSVnFi41O0Nl5ES7sLXydYkodXqHNE4sz2 0OhtLV/NCR9redRqPEwUQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:PSU3dTUT/rA=:1zs+7DbJK461en5dlqbANA jntzxMsoQzmeWRPXQoKL3IiBTE4aIQWS6RKoASKv5quoW09Z7ELx++Blsi9zzp4NLECg8+0qS 7LI317rjQeV//rneB5lXGZHrZoYVjGI1j+90TAxIrhrItN5SgoKuAkmlavwxYnS2wK/IayXJu 4ocndhEHhNa0tqZyo00wP3b+hP/55QjIeCZhdNFGxrUhdWCWxT4YC6wSAXwXyJEmy+FkOfhuq Cxuq9pToB6xBeOtnwx0i0kyNqUEnx8LTiqOc4TwTCTQmJZBTb+4Ew2mcIRVSaxHG0IZZgAWr4 YvjgM34WyhJ0zfDaliT3Xtuj6yZfWNu8bDKIfym0rwsaqB67ASENsIcKRQE+m4zOYXMkj2Bfx 4NbcWT8mJ4x95t9UHDmsb1HtD6EUENki5t+JcVlgB6xTJbEbXYXR7+xcFMaIw2WAiHEJwjl13 RhvcSKmq+hc/Scy+yvr+XQ1yOORCsCgWBMdbwla6Inv9DIp/P981V01SZ0esr1Kn2Qb5OQf3Y UaBu541YCWhFUPMwbgT1zVnB3b6AQD4DtHH6r0Xzi8yE0Yw7d3I2dI7p/LRMeNRXAyV9gywye /m7msqEiT1fvGE0wlCfro3K6oY+5GXG/+Y3K/bBhwPHMPL/Cixlg51T9JlGLur0atP9lQoEZW 05r+dsZgzHqCyw3E5g3XKQN9iu2qyEnDDd66AZ5SrdayhxNLTYPe5pzqervZNAYIsKDMOBBd/ 0iTdS9MdQeJCGM7FhMdMq4bbSOx9abLHxtUA47lInTDKCEj5XTU3RBdEljBeE0ql+2G+J98dH aO9BXdVD+CiNSXCYsYHt1LxKokn2NqeSZzMEDqq/muepdkRqL19CuSUSxh39uxmtH2mn2jwuT TDxGX+I+eaXa+rQ8RL8Q== Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2020-10-26 at 18:31 +0100, Sebastian Andrzej Siewior wrote: > On 2020-10-24 13:00:00 [+0800], Hillf Danton wrote: > > > > Hmm...curious how that word went into your mind. And when? > > > [ 30.457363] > > > other info that might help us debug this: > > > [ 30.457369] Possible unsafe locking scenario: > > > > > > [ 30.457375] CPU0 > > > [ 30.457378] ---- > > > [ 30.457381] lock(&mgr->vm_lock); > > > [ 30.457386] > > > [ 30.457389] lock(&mgr->vm_lock); > > > [ 30.457394] > > > *** DEADLOCK *** > > > > > > > > The backtrace contained the "normal" vm_lock. What should follow is the > backtrace of the in-softirq usage. > > > > > Dunno if blocking softint is a right cure. > > > > --- a/drivers/gpu/drm/drm_vma_manager.c > > +++ b/drivers/gpu/drm/drm_vma_manager.c > > @@ -229,6 +229,7 @@ EXPORT_SYMBOL(drm_vma_offset_add); > > void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr, > > struct drm_vma_offset_node *node) > > { > > + local_bh_disable(); > > There is write_lock_bh(). However changing only one will produce the > same backtrace somewhere else unless all other users already run BH > disabled region. Since there doesn't _seems_ to be a genuine deadlock lurking, I just asked lockdep to please not log the annoying initialization time chain. =2D-- a/drivers/gpu/drm/nouveau/nvkm/subdev/pci/base.c +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/pci/base.c @@ -116,7 +116,17 @@ nvkm_pci_oneinit(struct nvkm_subdev *sub return ret; } + /* + * Scheduler code taking cpuset_rwsem during irq thread initialization s= ets + * up a cpuset_rwsem vs mm->mmap_lock circular dependency gripe upon lat= er + * cpuset usage. It's harmless, tell lockdep there's nothing to see here= . + */ + if (force_irqthreads) + lockdep_off(); ret =3D request_irq(pdev->irq, nvkm_pci_intr, IRQF_SHARED, "nvkm", pci); + if (force_irqthreads) + lockdep_on(); + if (ret) return ret;