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: 582154 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 26D1F140BE0 for ; Fri, 12 Feb 2016 23:23:00 +1100 (AEDT) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id EE5AF1A00B6 for ; Fri, 12 Feb 2016 23:22:59 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Received: from e06smtp14.uk.ibm.com (e06smtp14.uk.ibm.com [195.75.94.110]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 5E8211A002B for ; Fri, 12 Feb 2016 23:21:59 +1100 (AEDT) Received: from localhost by e06smtp14.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: 16021212-0017-0000-0000-00000725A9FD X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Linux on PowerPC Developers Mail List 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 , linuxppc-dev@lists.ozlabs.org, Will Deacon , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Paul Mackerras , "Aneesh Kumar K.V" , Martin Schwidefsky , "Kirill A. Shutemov" , Andrew Morton , Linus Torvalds , Gerald Schaefer Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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