Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752040AbdGAQ3B (ORCPT ); Sat, 1 Jul 2017 12:29:01 -0400 Received: from mail-lf0-f68.google.com ([209.85.215.68]:35565 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751871AbdGAQ3A (ORCPT ); Sat, 1 Jul 2017 12:29:00 -0400 Date: Sat, 1 Jul 2017 19:28:56 +0300 From: Vladimir Davydov To: Sahitya Tummala Cc: Alexander Polakov , Andrew Morton , Jan Kara , viro@zeniv.linux.org.uk, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v4 2/2] fs/dcache.c: fix spin lockup issue on nlru->lock Message-ID: <20170701162856.i7ysaqb5s24hqero@esperanza> References: <20170628171854.t4sjyjv55j673qzv@esperanza> <1498707575-2472-1-git-send-email-stummala@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1498707575-2472-1-git-send-email-stummala@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1945 Lines: 45 On Thu, Jun 29, 2017 at 09:09:35AM +0530, Sahitya Tummala wrote: > __list_lru_walk_one() acquires nlru spin lock (nlru->lock) for > longer duration if there are more number of items in the lru list. > As per the current code, it can hold the spin lock for upto maximum > UINT_MAX entries at a time. So if there are more number of items in > the lru list, then "BUG: spinlock lockup suspected" is observed in > the below path - > > [] spin_bug+0x90 > [] do_raw_spin_lock+0xfc > [] _raw_spin_lock+0x28 > [] list_lru_add+0x28 > [] dput+0x1c8 > [] path_put+0x20 > [] terminate_walk+0x3c > [] path_lookupat+0x100 > [] filename_lookup+0x6c > [] user_path_at_empty+0x54 > [] SyS_faccessat+0xd0 > [] el0_svc_naked+0x24 > > This nlru->lock is acquired by another CPU in this path - > > [] d_lru_shrink_move+0x34 > [] dentry_lru_isolate_shrink+0x48 > [] __list_lru_walk_one.isra.10+0x94 > [] list_lru_walk_node+0x40 > [] shrink_dcache_sb+0x60 > [] do_remount_sb+0xbc > [] do_emergency_remount+0xb0 > [] process_one_work+0x228 > [] worker_thread+0x2e0 > [] kthread+0xf4 > [] ret_from_fork+0x10 > > Fix this lockup by reducing the number of entries to be shrinked > from the lru list to 1024 at once. Also, add cond_resched() before > processing the lru list again. > > Link: http://marc.info/?t=149722864900001&r=1&w=2 > Fix-suggested-by: Jan kara > Fix-suggested-by: Vladimir Davydov > Signed-off-by: Sahitya Tummala Acked-by: Vladimir Davydov