From patchwork Fri Sep 8 18:06:59 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Dufour X-Patchwork-Id: 811801 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [103.22.144.68]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3xpmft5Vx5z9sRV for ; Sat, 9 Sep 2017 04:53:10 +1000 (AEST) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 3xpmft3zTnzDrb2 for ; Sat, 9 Sep 2017 04:53:10 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=linux.vnet.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=ldufour@linux.vnet.ibm.com; receiver=) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xplfy5SmVzDrVj for ; Sat, 9 Sep 2017 04:08:10 +1000 (AEST) Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v88I4P5g013544 for ; Fri, 8 Sep 2017 14:08:08 -0400 Received: from e06smtp13.uk.ibm.com (e06smtp13.uk.ibm.com [195.75.94.109]) by mx0b-001b2d01.pphosted.com with ESMTP id 2cux39p4ss-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 08 Sep 2017 14:08:07 -0400 Received: from localhost by e06smtp13.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 8 Sep 2017 19:08:05 +0100 Received: from b06cxnps3074.portsmouth.uk.ibm.com (9.149.109.194) by e06smtp13.uk.ibm.com (192.168.101.143) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Fri, 8 Sep 2017 19:07:58 +0100 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v88I7wCO23593102; Fri, 8 Sep 2017 18:07:58 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8C90F4203F; Fri, 8 Sep 2017 19:04:25 +0100 (BST) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 53F4E42042; Fri, 8 Sep 2017 19:04:22 +0100 (BST) Received: from nimbus.lab.toulouse-stg.fr.ibm.com (unknown [9.145.31.125]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 8 Sep 2017 19:04:22 +0100 (BST) From: Laurent Dufour To: paulmck@linux.vnet.ibm.com, peterz@infradead.org, akpm@linux-foundation.org, kirill@shutemov.name, ak@linux.intel.com, mhocko@kernel.org, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky Subject: [PATCH v3 15/20] mm: Try spin lock in speculative path Date: Fri, 8 Sep 2017 20:06:59 +0200 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1504894024-2750-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1504894024-2750-1-git-send-email-ldufour@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17090818-0012-0000-0000-00000577A9AD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17090818-0013-0000-0000-000018F0B12A Message-Id: <1504894024-2750-16-git-send-email-ldufour@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-09-08_12:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1709080270 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, npiggin@gmail.com, linux-mm@kvack.org, Tim Chen , haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" There is a deadlock when a CPU is doing a speculative page fault and another one is calling do_unmap(). The deadlock occurred because the speculative path try to spinlock the pte while the interrupt are disabled. When the other CPU in the unmap's path has locked the pte then is waiting for all the CPU to invalidate the TLB. As the CPU doing the speculative fault have the interrupt disable it can't invalidate the TLB, and can't get the lock. Since we are in a speculative path, we can race with other mm action. So let assume that the lock may not get acquired and fail the speculative page fault. Here are the stacks captured during the deadlock: CPU 0 native_flush_tlb_others+0x7c/0x260 flush_tlb_mm_range+0x6a/0x220 tlb_flush_mmu_tlbonly+0x63/0xc0 unmap_page_range+0x897/0x9d0 ? unmap_single_vma+0x7d/0xe0 ? release_pages+0x2b3/0x360 unmap_single_vma+0x7d/0xe0 unmap_vmas+0x51/0xa0 unmap_region+0xbd/0x130 do_munmap+0x279/0x460 SyS_munmap+0x53/0x70 CPU 1 do_raw_spin_lock+0x14e/0x160 _raw_spin_lock+0x5d/0x80 ? pte_map_lock+0x169/0x1b0 pte_map_lock+0x169/0x1b0 handle_pte_fault+0xbf2/0xd80 ? trace_hardirqs_on+0xd/0x10 handle_speculative_fault+0x272/0x280 handle_speculative_fault+0x5/0x280 __do_page_fault+0x187/0x580 trace_do_page_fault+0x52/0x260 do_async_page_fault+0x19/0x70 async_page_fault+0x28/0x30 Signed-off-by: Laurent Dufour --- mm/memory.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 5e98259c7ac0..18b39f930ce1 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2432,7 +2432,8 @@ static bool pte_spinlock(struct vm_fault *vmf) goto out; vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); - spin_lock(vmf->ptl); + if (unlikely(!spin_trylock(vmf->ptl))) + goto out; if (vma_has_changed(vmf)) { spin_unlock(vmf->ptl); @@ -2468,8 +2469,20 @@ static bool pte_map_lock(struct vm_fault *vmf) if (vma_has_changed(vmf)) goto out; - pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, - vmf->address, &ptl); + /* + * Same as pte_offset_map_lock() except that we call + * spin_trylock() in place of spin_lock() to avoid race with + * unmap path which may have the lock and wait for this CPU + * to invalidate TLB but this CPU has irq disabled. + * Since we are in a speculative patch, accept it could fail + */ + ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); + pte = pte_offset_map(vmf->pmd, vmf->address); + if (unlikely(!spin_trylock(ptl))) { + pte_unmap(pte); + goto out; + } + if (vma_has_changed(vmf)) { pte_unmap_unlock(pte, ptl); goto out;