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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 054F4C2BB55 for ; Fri, 10 Apr 2020 09:08:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C468720801 for ; Fri, 10 Apr 2020 09:08:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586509723; bh=vveq8hq4tZ4KJEkqR2DPVe2ODOea/E2UKD483B1OMqI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=WDVetHz7okuhSILrXzoQgpCquvUQ8iBscxx+vT0ZMF5/YU7stIhmXkj9HA8yHjVes 6D5v7bMZpyaUvgB2e/hHmpz62NOh9k1JUj/Et2lHQ55wmHr7ZKybkkhoKi8LgxkRtM NskxUbnGnqhZp3XOvbPbkkEj1uFPYxHxpp3nQYl0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725893AbgDJJIm (ORCPT ); Fri, 10 Apr 2020 05:08:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:40424 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725858AbgDJJIm (ORCPT ); Fri, 10 Apr 2020 05:08:42 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 9DA44206F7; Fri, 10 Apr 2020 09:08:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586509721; bh=vveq8hq4tZ4KJEkqR2DPVe2ODOea/E2UKD483B1OMqI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hfXrj0TKtmzmyGTpTS6yZPQPvGrK5/rDkwRaELSo41Vc7PKlEbCsOL4vYTwiztZvf SGeMGSTStb3bsOpfqFmz8O3DFtFBM6BrMKxN1sXWiXX0NmcATYnFJADWkpM9wQSuzx ozrElzpwYOAY/BtU6FcpMSm2pN4u2lB3+BdSIANE= Date: Fri, 10 Apr 2020 11:08:38 +0200 From: Greg KH To: Sultan Alsawaf Cc: stable@vger.kernel.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter , Chris Wilson , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH v2] drm/i915: Fix ref->mutex deadlock in i915_active_wait() Message-ID: <20200410090838.GD1691838@kroah.com> References: <20200407065210.GA263852@kroah.com> <20200407071809.3148-1-sultan@kerneltoast.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200407071809.3148-1-sultan@kerneltoast.com> Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Apr 07, 2020 at 12:18:09AM -0700, Sultan Alsawaf wrote: > From: Sultan Alsawaf > > The following deadlock exists in i915_active_wait() due to a double lock > on ref->mutex (call chain listed in order from top to bottom): > i915_active_wait(); > mutex_lock_interruptible(&ref->mutex); <-- ref->mutex first acquired > i915_active_request_retire(); > node_retire(); > active_retire(); > mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING); <-- DEADLOCK > > Fix the deadlock by skipping the second ref->mutex lock when > active_retire() is called through i915_active_request_retire(). > > Note that this bug only affects 5.4 and has since been fixed in 5.5. > Normally, a backport of the fix from 5.5 would be in order, but the > patch set that fixes this deadlock involves massive changes that are > neither feasible nor desirable for backporting [1][2][3]. Therefore, > this small patch was made to address the deadlock specifically for 5.4. > > [1] 274cbf20fd10 ("drm/i915: Push the i915_active.retire into a worker") > [2] 093b92287363 ("drm/i915: Split i915_active.mutex into an irq-safe spinlock for the rbtree") > [3] 750bde2fd4ff ("drm/i915: Serialise with remote retirement") > > Fixes: 12c255b5dad1 ("drm/i915: Provide an i915_active.acquire callback") > Cc: # 5.4.x > Signed-off-by: Sultan Alsawaf > --- > drivers/gpu/drm/i915/i915_active.c | 27 +++++++++++++++++++++++---- > drivers/gpu/drm/i915/i915_active.h | 4 ++-- > 2 files changed, 25 insertions(+), 6 deletions(-) Now queued up, thanks. greg k-h