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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 921FECA9EBD for ; Sat, 26 Oct 2019 13:18:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 67D5C222C1 for ; Sat, 26 Oct 2019 13:18:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572095901; bh=Da2+BDVNfV3cOEI+tV/Lq5ouvPU5Dta7w1CoeLfooqw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=jHEynE9vDjl247Klyy3WtvzNcWJsca6C6NgE9ejDphJ3M5tG4klp5bjPjp9zbdmyG mrAwxW/JYv6JRJwxR4hACqBX4INsHoh4nBfYfnP+++sWZOnHpXpiOSU8F8rWCxlmk3 D6BEyVIlnXEjd4Z/r6jg8oek5rbcwhUUCEmPzzLY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726476AbfJZNSU (ORCPT ); Sat, 26 Oct 2019 09:18:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:39954 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727757AbfJZNSQ (ORCPT ); Sat, 26 Oct 2019 09:18:16 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BECD721E6F; Sat, 26 Oct 2019 13:18:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572095895; bh=Da2+BDVNfV3cOEI+tV/Lq5ouvPU5Dta7w1CoeLfooqw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SXKOwjtgV7m3nBjnqmfJ2Gj46RhpBpsbzI9NF0ZlNKZZStGVlQc6eqYRHfjB68kqA iuvUr+OpxX4g2BztYk6G7IpWB55DTkwX/jnrIDPRYOcYofyCwACkJ8f7PSg0nFCbNH 49MsK/zqi0rCt6Q6qYPmBfZyl+e1F44BQ1P1RYas= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Linus Torvalds , Dmitry V Levin , Anatoly Pugachev , Meelis Roos , Christoph Hellwig , David Miller , Sasha Levin , sparclinux@vger.kernel.org Subject: [PATCH AUTOSEL 5.3 77/99] sparc64: disable fast-GUP due to unexplained oopses Date: Sat, 26 Oct 2019 09:15:38 -0400 Message-Id: <20191026131600.2507-77-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191026131600.2507-1-sashal@kernel.org> References: <20191026131600.2507-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Linus Torvalds [ Upstream commit 8e0d0ad206f08506c893326ca7c9c3d9cc042cef ] HAVE_FAST_GUP enables the lockless quick page table walker for simple cases, and is a nice optimization for some random loads that can then use get_user_pages_fast() rather than the more careful page walker. However, for some unexplained reason, it seems to be subtly broken on sparc64. The breakage is only with some compiler versions and some hardware, and nobody seems to have figured out what triggers it, although there's a simple reprodicer for the problem when it does trigger. The problem was introduced with the conversion to the generic GUP code in commit 7b9afb86b632 ("sparc64: use the generic get_user_pages_fast code"), but nothing looks obviously wrong in that conversion. It may be a compiler bug that just hits us with the code reorganization. Or it may be something very specific to sparc64. This disables HAVE_FAST_GUP entirely. That makes things like futexes a bit slower, but at least they work. If we can figure out the trigger, that would be lovely, but it's been three months already.. Link: https://lore.kernel.org/lkml/20190717215956.GA30369@altlinux.org/ Fixes: 7b9afb86b632 ("sparc64: use the generic get_user_pages_fast code") Reported-by: Dmitry V Levin Reported-by: Anatoly Pugachev Requested-by: Meelis Roos Suggested-by: Christoph Hellwig Cc: David Miller Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- arch/sparc/Kconfig | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index 7926a2e11bdc2..6a31f240840d4 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -28,7 +28,6 @@ config SPARC select RTC_DRV_M48T59 select RTC_SYSTOHC select HAVE_ARCH_JUMP_LABEL if SPARC64 - select HAVE_FAST_GUP if SPARC64 select GENERIC_IRQ_SHOW select ARCH_WANT_IPC_PARSE_VERSION select GENERIC_PCI_IOMAP -- 2.20.1