From patchwork Fri Feb 12 12:21:46 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Ott X-Patchwork-Id: 8290521 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 9892ABEEE5 for ; Fri, 12 Feb 2016 12:25:19 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id ABA57203AC for ; Fri, 12 Feb 2016 12:25:18 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C4DC020211 for ; Fri, 12 Feb 2016 12:25:17 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1aUCju-0005FN-PM; Fri, 12 Feb 2016 12:22:22 +0000 Received: from e06smtp10.uk.ibm.com ([195.75.94.106]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1aUCjr-00052z-Bg for linux-arm-kernel@lists.infradead.org; Fri, 12 Feb 2016 12:22:20 +0000 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Shutemov" Subject: Re: [BUG] random kernel crashes after THP rework on s390 (maybe also on PowerPC and ARM) In-Reply-To: <20160211191253.GA8589@black.fi.intel.com> Message-ID: References: <20160211192223.4b517057@thinkpad> <20160211190942.GA10244@node.shutemov.name> <20160211191253.GA8589@black.fi.intel.com> User-Agent: Alpine 2.20 (LFD 67 2015-01-07) Organization: =?ISO-8859-15?Q?=22IBM_Deutschland_Research_&_Development_GmbH_=2F_Vorsitzende_des_Aufsichtsrats=3A_Martina_Koederitz_Gesch=E4ftsf=FChrung=3A_Dirk_Wittkopp_Sitz_der_Gesellschaft=3A_B=F6blingen_=2F_Registergericht?= =?ISO-8859-15?Q?=3A_Amtsgericht_Stuttgart=2C_HRB_243294=22?= MIME-Version: 1.0 X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16021212-0041-0000-0000-0000073F986A X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160212_042219_720764_253F3B22 X-CRM114-Status: GOOD ( 23.33 ) X-Spam-Score: -4.5 (----) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, Catalin Marinas , Heiko Carstens , Michael Ellerman , linuxppc-dev@lists.ozlabs.org, Will Deacon , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Paul Mackerras , "Aneesh Kumar K.V" , Benjamin Herrenschmidt , Martin Schwidefsky , "Kirill A. Shutemov" , Andrew Morton , Linus Torvalds , Gerald Schaefer Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Thu, 11 Feb 2016, Kirill A. Shutemov wrote: > On Thu, Feb 11, 2016 at 09:09:42PM +0200, Kirill A. Shutemov wrote: > > On Thu, Feb 11, 2016 at 07:22:23PM +0100, Gerald Schaefer wrote: > > > Hi, > > > > > > Sebastian Ott reported random kernel crashes beginning with v4.5-rc1 and > > > he also bisected this to commit 61f5d698 "mm: re-enable THP". Further > > > review of the THP rework patches, which cannot be bisected, revealed > > > commit fecffad "s390, thp: remove infrastructure for handling splitting PMDs" > > > (and also similar commits for other archs). > > > > > > This commit removes the THP splitting bit and also the architecture > > > implementation of pmdp_splitting_flush(), which took care of the IPI for > > > fast_gup serialization. The commit message says > > > > > > pmdp_splitting_flush() is not needed too: on splitting PMD we will do > > > pmdp_clear_flush() + set_pte_at(). pmdp_clear_flush() will do IPI as > > > needed for fast_gup > > > > > > The assumption that a TLB flush will also produce an IPI is wrong on s390, > > > and maybe also on other architectures, and I thought that this was actually > > > the main reason for having an arch-specific pmdp_splitting_flush(). > > > > > > At least PowerPC and ARM also had an individual implementation of > > > pmdp_splitting_flush() that used kick_all_cpus_sync() instead of a TLB > > > flush to send the IPI, and those were also removed. Putting the arch > > > maintainers and mailing lists on cc to verify. > > > > > > On s390 this will break the IPI serialization against fast_gup, which > > > would certainly explain the random kernel crashes, please revert or fix > > > the pmdp_splitting_flush() removal. > > > > Sorry for that. > > > > I believe, the problem was already addressed for PowerPC: > > > > http://lkml.kernel.org/g/454980831-16631-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com > > Correct link is > > http://lkml.kernel.org/g/1454980831-16631-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com > Based on your suggestion Gerald provided the following patch but sadly it didn't fix the problem. Sebastian --- arch/s390/include/asm/pgtable.h | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -1587,6 +1587,8 @@ static inline void pmdp_invalidate(struc unsigned long address, pmd_t *pmdp) { pmdp_flush_direct(vma->vm_mm, address, pmdp); + /* Serialize against fast_gup with IPI */ + kick_all_cpus_sync(); } #define __HAVE_ARCH_PMDP_SET_WRPROTECT