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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 159E4C2BA19 for ; Tue, 14 Apr 2020 08:23:48 +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 DBD0C2074D for ; Tue, 14 Apr 2020 08:23:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="ssSnRykY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DBD0C2074D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 49E0189E06; Tue, 14 Apr 2020 08:23:47 +0000 (UTC) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8554E89E06; Tue, 14 Apr 2020 08:23:46 +0000 (UTC) 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 D64B8206E9; Tue, 14 Apr 2020 08:23:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586852626; bh=XTiMmTH7ku2PD1MJtQxAEiKXyWDrEBK4t5m1ytbJcPA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ssSnRykYbxlsPu9UVRRbqnPk5oRim164zBpl5ZvjSdBABRjQbs9PfN5ITaXonzayx jQW/IWgUcfvTlXF85yfu7D6icnRVxbROCVV+DEG63KgkeAhmcOLrLlx5w1kLUyefXV vYOqsrIys2LhFwIETqckAQ9M2bIhEtGw+qJ6592I= Date: Tue, 14 Apr 2020 10:23:44 +0200 From: Greg KH To: Chris Wilson Subject: Re: [PATCH v2] drm/i915: Fix ref->mutex deadlock in i915_active_wait() Message-ID: <20200414082344.GA10645@kroah.com> References: <20200407065210.GA263852@kroah.com> <20200407071809.3148-1-sultan@kerneltoast.com> <20200410090838.GD1691838@kroah.com> <20200410141738.GB2025@sultan-box.localdomain> <20200411113957.GB2606747@kroah.com> <158685210730.16269.15932754047962572236@build.alporthouse.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <158685210730.16269.15932754047962572236@build.alporthouse.com> 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: , Cc: dri-devel@lists.freedesktop.org, David Airlie , intel-gfx@lists.freedesktop.org, stable@vger.kernel.org, Rodrigo Vivi , Sultan Alsawaf Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, Apr 14, 2020 at 09:15:07AM +0100, Chris Wilson wrote: > Quoting Greg KH (2020-04-11 12:39:57) > > On Fri, Apr 10, 2020 at 07:17:38AM -0700, Sultan Alsawaf wrote: > > > On Fri, Apr 10, 2020 at 11:08:38AM +0200, Greg KH wrote: > > > > 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 > > > > > > I'm sorry, I meant the v3 [1]. Apologies for the confusion. The v3 was picked > > > into Ubuntu so that's what we're rolling with. > > > > Ok, thanks, hopefully now I picked upthe right one... > > The patch does not fix a deadlock. Greg, this patch is not a backport of > a bugfix, why is it in stable? Because it says it can't be a backport as the 3 above mentioned patches do the same thing instead? I will be glad to drop this, but I need some kind of direction here, and given that at least one distro is already shipping this, it felt like the correct thing to do. So, what do you want me to do? thanks, greg k-h _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel 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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 84D7EC352B6 for ; Tue, 14 Apr 2020 08:23:49 +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 59C992074D for ; Tue, 14 Apr 2020 08:23:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="ssSnRykY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 59C992074D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 79E8189E23; Tue, 14 Apr 2020 08:23:47 +0000 (UTC) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8554E89E06; Tue, 14 Apr 2020 08:23:46 +0000 (UTC) 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 D64B8206E9; Tue, 14 Apr 2020 08:23:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586852626; bh=XTiMmTH7ku2PD1MJtQxAEiKXyWDrEBK4t5m1ytbJcPA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ssSnRykYbxlsPu9UVRRbqnPk5oRim164zBpl5ZvjSdBABRjQbs9PfN5ITaXonzayx jQW/IWgUcfvTlXF85yfu7D6icnRVxbROCVV+DEG63KgkeAhmcOLrLlx5w1kLUyefXV vYOqsrIys2LhFwIETqckAQ9M2bIhEtGw+qJ6592I= Date: Tue, 14 Apr 2020 10:23:44 +0200 From: Greg KH To: Chris Wilson Message-ID: <20200414082344.GA10645@kroah.com> References: <20200407065210.GA263852@kroah.com> <20200407071809.3148-1-sultan@kerneltoast.com> <20200410090838.GD1691838@kroah.com> <20200410141738.GB2025@sultan-box.localdomain> <20200411113957.GB2606747@kroah.com> <158685210730.16269.15932754047962572236@build.alporthouse.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <158685210730.16269.15932754047962572236@build.alporthouse.com> Subject: Re: [Intel-gfx] [PATCH v2] drm/i915: Fix ref->mutex deadlock in i915_active_wait() X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dri-devel@lists.freedesktop.org, David Airlie , intel-gfx@lists.freedesktop.org, stable@vger.kernel.org, Sultan Alsawaf Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Tue, Apr 14, 2020 at 09:15:07AM +0100, Chris Wilson wrote: > Quoting Greg KH (2020-04-11 12:39:57) > > On Fri, Apr 10, 2020 at 07:17:38AM -0700, Sultan Alsawaf wrote: > > > On Fri, Apr 10, 2020 at 11:08:38AM +0200, Greg KH wrote: > > > > 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 > > > > > > I'm sorry, I meant the v3 [1]. Apologies for the confusion. The v3 was picked > > > into Ubuntu so that's what we're rolling with. > > > > Ok, thanks, hopefully now I picked upthe right one... > > The patch does not fix a deadlock. Greg, this patch is not a backport of > a bugfix, why is it in stable? Because it says it can't be a backport as the 3 above mentioned patches do the same thing instead? I will be glad to drop this, but I need some kind of direction here, and given that at least one distro is already shipping this, it felt like the correct thing to do. So, what do you want me to do? thanks, greg k-h _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx 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,URIBL_BLOCKED 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 909F1C2BA19 for ; Tue, 14 Apr 2020 08:24:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D3E8206E9 for ; Tue, 14 Apr 2020 08:24:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586852640; bh=XTiMmTH7ku2PD1MJtQxAEiKXyWDrEBK4t5m1ytbJcPA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Fp7KsHjPQp8dmAnKK/zkdOA28x9DuprMD/nSmd9uiNiAdflvvIxnPUwn7nqQoU9RA OYt9wizMAQhVXpzBnL5k9pts4bmclWHh1455qbYvqOKNStab0bQEH6rbXFH3jIsq6X J0ayEE9xJYfDjjmMa/pgLMxpz20o8wXWpsTSiMbg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436648AbgDNIXv (ORCPT ); Tue, 14 Apr 2020 04:23:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:35984 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2436643AbgDNIXq (ORCPT ); Tue, 14 Apr 2020 04:23:46 -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 D64B8206E9; Tue, 14 Apr 2020 08:23:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586852626; bh=XTiMmTH7ku2PD1MJtQxAEiKXyWDrEBK4t5m1ytbJcPA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ssSnRykYbxlsPu9UVRRbqnPk5oRim164zBpl5ZvjSdBABRjQbs9PfN5ITaXonzayx jQW/IWgUcfvTlXF85yfu7D6icnRVxbROCVV+DEG63KgkeAhmcOLrLlx5w1kLUyefXV vYOqsrIys2LhFwIETqckAQ9M2bIhEtGw+qJ6592I= Date: Tue, 14 Apr 2020 10:23:44 +0200 From: Greg KH To: Chris Wilson Cc: Sultan Alsawaf , stable@vger.kernel.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter , 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: <20200414082344.GA10645@kroah.com> References: <20200407065210.GA263852@kroah.com> <20200407071809.3148-1-sultan@kerneltoast.com> <20200410090838.GD1691838@kroah.com> <20200410141738.GB2025@sultan-box.localdomain> <20200411113957.GB2606747@kroah.com> <158685210730.16269.15932754047962572236@build.alporthouse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158685210730.16269.15932754047962572236@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 09:15:07AM +0100, Chris Wilson wrote: > Quoting Greg KH (2020-04-11 12:39:57) > > On Fri, Apr 10, 2020 at 07:17:38AM -0700, Sultan Alsawaf wrote: > > > On Fri, Apr 10, 2020 at 11:08:38AM +0200, Greg KH wrote: > > > > 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 > > > > > > I'm sorry, I meant the v3 [1]. Apologies for the confusion. The v3 was picked > > > into Ubuntu so that's what we're rolling with. > > > > Ok, thanks, hopefully now I picked upthe right one... > > The patch does not fix a deadlock. Greg, this patch is not a backport of > a bugfix, why is it in stable? Because it says it can't be a backport as the 3 above mentioned patches do the same thing instead? I will be glad to drop this, but I need some kind of direction here, and given that at least one distro is already shipping this, it felt like the correct thing to do. So, what do you want me to do? thanks, greg k-h