From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758648AbdAJJYU (ORCPT ); Tue, 10 Jan 2017 04:24:20 -0500 Received: from mx2.suse.de ([195.135.220.15]:37084 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751859AbdAJJWn (ORCPT ); Tue, 10 Jan 2017 04:22:43 -0500 Date: Tue, 10 Jan 2017 10:22:41 +0100 From: Michal Hocko To: Sami Farin Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [BUG] How to crash 4.9.2 x86_64: vmscan: shrink_slab Message-ID: <20170110092241.GA28032@dhcp22.suse.cz> References: <20170109210210.2zgvw6nfs4qbgmjw@m.mifar.in> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170109210210.2zgvw6nfs4qbgmjw@m.mifar.in> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 09-01-17 23:02:10, Sami Farin wrote: > # sysctl vm.vfs_cache_pressure=-100 > > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6640827866535449472 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6640827866535450112 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-661702561611775889 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6640827866535442432 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6562613194205300197 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6640827866535439872 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-659655090764208789 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6564660665198832072 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6562613194351275164 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6562615996648922728 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6564660665198832072 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-6562613194351264981 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-569296135781119076 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-565206492037048430 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-565212096665106188 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-569296135781119076 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-565206492037043196 > kernel: vmscan: shrink_slab: super_cache_scan+0x0/0x1a0 negative objects to delete nr=-659660388715270673 > > > Alternatively, > # sysctl vm.vfs_cache_pressure=10000000 Both values are insane and admins do not do insane things to their machines, do they? I am not sure how much we want to check the input value. -100 is clearly bogus and .procname = "vfs_cache_pressure", .data = &sysctl_vfs_cache_pressure, .maxlen = sizeof(sysctl_vfs_cache_pressure), .mode = 0644, .proc_handler = &proc_dointvec, .extra1 = &zero, tries to enforce min (extra1) check except proc_dointvec doesn't care about this... This is news to me. Only proc_dointvec_minmax does care about extra*, it seems. -- Michal Hocko SUSE Labs