From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751282AbcGNLVa (ORCPT ); Thu, 14 Jul 2016 07:21:30 -0400 Received: from bourbon.biscuit.ninja ([91.239.64.50]:38618 "EHLO bourbon.biscuit.ninja" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750862AbcGNLV1 (ORCPT ); Thu, 14 Jul 2016 07:21:27 -0400 X-Greylist: delayed 507 seconds by postgrey-1.27 at vger.kernel.org; Thu, 14 Jul 2016 07:21:27 EDT Message-ID: <1468494776.3175.5.camel@cinelli.bikeshed.internal> Subject: RE: [RFC PATCH] dcache: give a chance to yield in shrink_dentry_list From: Biscuit Ninja To: linux-kernel@vger.kernel.org Date: Thu, 14 Jul 2016 12:12:56 +0100 Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > A softlockup in shrink_dentry_list when called from shrink_dcache_sb > was observed on a very busy server. It's possible that the list > passed to shrink_dentry_list is so big that it takes a while to > dispose of all entries. Adding a simple cond_resched would give > the cpu a chance to do some other useful work and no trip the > softlockup watchdog. Hello Nikolay, I'm interested in your proposed patch because I believe I've come across the same issue a handful of times, typically: WARNING: CPU: 0 PID: 22717 at /build/buildd/linux-lts-trusty-3.13.0/fs/dcache.c:362 d_shrink_del +0x79/0x90() Modules linked in: pcnet32 mii vmwgfx ttm drm psmouse lp i2c_piix4 ppdev parport_pc vmw_vmci shpchp serio_raw mac_hid vmw_balloon parport floppy mptspi mptscsih mptbase e1000 vmw_pvscsi vmxnet3 CPU: 0 PID: 22717 Comm: sh Not tainted 3.13.0-32-generic #57~precise1-Ubuntu Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 10/22/2013 000000000000016a ffff88000616bbe8 ffffffff81752c9e 0000000000000007 0000000000000000 ffff88000616bc28 ffffffff8106af7c ffff88000616bc08 ffff880037f54480 ffff880037f54480 ffff880037f54500 ffff880037f544d8 Call Trace: [] dump_stack+0x46/0x58 [] warn_slowpath_common+0x8c/0xc0 [] warn_slowpath_null+0x1a/0x20 [] d_shrink_del+0x79/0x90 [] shrink_dentry_list+0x62/0xe0 [] shrink_dcache_parent+0x28/0x70 [] proc_flush_task_mnt.isra.15+0x77/0x170 [] proc_flush_task+0x56/0x70 [] release_task+0x33/0x130 [] wait_task_zombie+0x4cf/0x5f0 [] wait_consider_task.part.8+0x10b/0x180 [] wait_consider_task+0x65/0x70 [] do_wait+0x101/0x260 [] SyS_wait4+0xa3/0x100 [] ? task_stopped_code+0x50/0x50 [] tracesys+0xe1/0xe6 ---[ end trace e2a4a7d8b698f0ea ]--- BUG: soft lockup - CPU#0 stuck for 22s! [sh:22717] Modules linked in: pcnet32 mii vmwgfx ttm drm psmouse lp i2c_piix4 ppdev parport_pc vmw_vmci shpchp serio_raw mac_hid vmw_balloon parport floppy mptspi mptscsih mptbase e1000 vmw_pvscsi vmxnet3 CPU: 0 PID: 22717 Comm: sh Tainted: G W 3.13.0-32-generic #57~precise1-Ubuntu Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 10/22/2013 task: ffff88001ef717f0 ti: ffff88000616a000 task.ti: ffff88000616a000 RIP: 0010:[] [] _raw_spin_lock +0x1c/0x50 RSP: 0018:ffff88000616bc58 EFLAGS: 00000246 This is under Ubuntu 12.04.5 with kernel 3.13.0-32-generic.