From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.13]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 20901212566; Mon, 25 May 2026 08:55:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.13 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779699356; cv=none; b=GpOVikN1p4hZGBFkDN+Yi+cbY7cueoAjlOM5KyOp4zYjX/6agiJfSaOB2TquPagtTpGD10BhTCAfbvmy07U+F/8DgIEIbWl56uK7srVmOdNBBiJnN9/BTGPoOFmKpY6AyDChYNvzf65S4Rbt8gm5ct461qbPZhsAXR6heNn7eRU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779699356; c=relaxed/simple; bh=QDVlHkaJzd1yhCNccg0oJiSTSQUYqwHGcctnwRzp9hY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JU1XUsu17uLdWLe5DGeUwLwZw+iGF8JxUVYE8n8/9wEDiMwHWlz5RQB7rdKACdeQ1uhnqNa2GlTWBYi5hDTlIRegT1j2gFOZHQIwh5tLKGTxUYkEnvQsU++bYD5L9ELdusuWG/uO0eQzeVL1DkzNx6A5r36Mdq9yOuM5YPnGnP0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=njjuR/c4; arc=none smtp.client-ip=198.175.65.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="njjuR/c4" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1779699354; x=1811235354; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=QDVlHkaJzd1yhCNccg0oJiSTSQUYqwHGcctnwRzp9hY=; b=njjuR/c45goQgObIEkONMk1GF73NqfGHRIkUYGs+y3vXgnnVbQqXR1H0 mggtZh9c0X7QMAt6uzy0Ku7ZayvPAChcDvEk8u1+MDb7gam03xz32VzIY gAUiqI8J25i6X/Z0BQ6c1RijLZTdp0DiPqpI5xBuE6aGc+EJZS7mf5WSI pBzBSqEz/UYBhfxfGFyXsg7UtRxjZTwarP/pp5usB+xwK5ZBPZKu5q8ZI iKC1nx89w3HSSeWBmuoJRaHqHv/BZXBP7H+oepXXsfgKXvTYxlP4VbPBl 1hES/44SAoeT5QaND/FWtG79U5usAM5Y9BJg6VWShrCS5xwjdbKMGVosq w==; X-CSE-ConnectionGUID: IEAedow2QDSpvom1YcsjXg== X-CSE-MsgGUID: Ho1rYmAATJq6Vj1+AKmCVg== X-IronPort-AV: E=McAfee;i="6800,10657,11796"; a="91627068" X-IronPort-AV: E=Sophos;i="6.24,167,1774335600"; d="scan'208";a="91627068" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 May 2026 01:55:51 -0700 X-CSE-ConnectionGUID: Bknsz68oR+KLd8gP4UuJog== X-CSE-MsgGUID: ZUe6382PRmebDTDU7tSw+w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,167,1774335600"; d="scan'208";a="237129261" Received: from pgcooper-mobl3.ger.corp.intel.com (HELO [10.245.245.200]) ([10.245.245.200]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 May 2026 01:55:47 -0700 Message-ID: <9c4a68c4-43a3-4a9b-a131-9570174c8df3@linux.intel.com> Date: Mon, 25 May 2026 10:55:43 +0200 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6.18.y] drm/vkms: Fix ABBA deadlock in vblank disable and timer callback To: w15303746062 , Greg KH Cc: louis.chauvet@bootlin.com, hamohammed.sa@gmail.com, simona@ffwll.ch, melissa.srw@gmail.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Mingyu Wang <25181214217@stu.xidian.edu.cn> References: <20260515131826.388154-1-w15303746062@163.com> <2026051557-thermal-petite-7da0@gregkh> <581657f0.ba8.19e2eaaf003.Coremail.w15303746062@163.com> <2026051633-skyward-parrot-cdd3@gregkh> <397754a7.224c.19e38e42006.Coremail.w15303746062@163.com> Content-Language: en-US From: Maarten Lankhorst In-Reply-To: <397754a7.224c.19e38e42006.Coremail.w15303746062@163.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hello Mingyu Den 2026-05-18 kl. 04:22, skrev w15303746062: > > > At 2026-05-16 17:51:59, "Greg KH" wrote: >> There is no "minimal-risk policy for stable trees". And if there was, >> the least ammount of risk would be to take the reviewed and tested >> patches that are already in Linus's tree, and NOT take anything that is >> not already there, as 90% of the time that we do that, it comes back to >> bite us hard. >> >> So please, just backport all the needed changes here. Otherwise how are >> we going to deal with the merge conflicts for the next 4 years in this >> file? >> >> Or, get the maintainers of this file to agree and review this one-off >> change that it is acceptable. As they are going to be the ones getting >> the bug reports and not having their patches applied over the years, not >> anyone else :) > > Hi Greg, > > Got it. After looking deeper into the dependency chain, backporting the mainline commit (02e2681ffe1a) would indeed require pulling in the entire new DRM generic vblank timer infrastructure to 6.18.y. > > That scope is just too large and complex for this specific issue. Since a one-off patch is not the right approach either, I will just drop this patch and abandon the backport effort for 6.18.y. > > Thanks for your time and the quick review. > > Thanks, > Mingyu > As far as I can tell, if it's just a bug affecting vkms, all you need to do is only a few commits: 74afeb812850 ("drm/vblank: Add vblank timer") d54dbb5963bd ("drm/vblank: Add CRTC helpers for simple use cases") 02e2681ffe1a ("drm/vkms: Convert to DRM's vblank timer") 79ae8510b5b8 ("drm/atomic: Increase timeout in drm_atomic_helper_wait_for_vblanks()") 3946d3ba9934 ("drm/vblank: Fix kernel docs for vblank timer") There's no need to convert all other drivers if it's only vkms that you're fixing. But since you found this bug in one driver, it might be wise to check if others have the same bug and ask for backports for those too. Kind regards, ~Maarten Lankhorst