From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751508AbeBTX6C (ORCPT ); Tue, 20 Feb 2018 18:58:02 -0500 Received: from out30-133.freemail.mail.aliyun.com ([115.124.30.133]:47258 "EHLO out30-133.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751312AbeBTX6B (ORCPT ); Tue, 20 Feb 2018 18:58:01 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07488;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0SyJ1.1w_1519171065; Subject: Re: [PATCH] fs: proc: use down_read_killable in proc_pid_cmdline_read() To: akpm@linux-foundation.org, mingo@kernel.org, adobriyan@gmail.com Cc: linux-kernel@vger.kernel.org References: <1519156169-11883-1-git-send-email-yang.shi@linux.alibaba.com> From: Yang Shi Message-ID: <6ff7bb3e-917d-121c-1972-7d9ba6139a35@linux.alibaba.com> Date: Tue, 20 Feb 2018 15:57:44 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <1519156169-11883-1-git-send-email-yang.shi@linux.alibaba.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/20/18 11:49 AM, Yang Shi wrote: > When running vm-scalability with large memory (> 300GB), the below hung > task issue happens occasionally. > > INFO: task ps:14018 blocked for more than 120 seconds. > Tainted: G E 4.9.79-009.ali3000.alios7.x86_64 #1 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > ps D 0 14018 1 0x00000004 > ffff885582f84000 ffff885e8682f000 ffff880972943000 ffff885ebf499bc0 > ffff8828ee120000 ffffc900349bfca8 ffffffff817154d0 0000000000000040 > 00ffffff812f872a ffff885ebf499bc0 024000d000948300 ffff880972943000 > Call Trace: > [] ? __schedule+0x250/0x730 > [] schedule+0x36/0x80 > [] rwsem_down_read_failed+0xf0/0x150 > [] call_rwsem_down_read_failed+0x18/0x30 > [] down_read+0x20/0x40 > [] proc_pid_cmdline_read+0xd9/0x4e0 > [] ? do_filp_open+0xa5/0x100 > [] __vfs_read+0x37/0x150 > [] ? security_file_permission+0x9b/0xc0 > [] vfs_read+0x96/0x130 > [] SyS_read+0x55/0xc0 > [] entry_SYSCALL_64_fastpath+0x1a/0xc5 > > When manipulating a large mapping, the process may hold the mmap_sem for > long time, so reading /proc//cmdline may be blocked in > uninterruptible state for long time. > > down_read_trylock() sounds too aggressive, and we already have killable > version APIs for semaphore, here use down_read_killable() to improve the > responsiveness. > > Signed-off-by: Yang Shi > Cc: Alexey Dobriyan > --- > fs/proc/base.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index 9298324..44b6f8f 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -242,7 +242,9 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, > goto out_mmput; > } > > - down_read(&mm->mmap_sem); > + rv = down_read_killable(&mm->mmap_sem); > + if (rv) > + goto out_mmput; > arg_start = mm->arg_start; > arg_end = mm->arg_end; > env_start = mm->env_start; Should goto out_free_page, amended patch as below. diff --git a/fs/proc/base.c b/fs/proc/base.c index 9298324..057e6bd 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -242,7 +242,9 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, goto out_mmput; } - down_read(&mm->mmap_sem); + rv = down_read_killable(&mm->mmap_sem); + if (rv) + goto out_free_page; arg_start = mm->arg_start; arg_end = mm->arg_end; env_start = mm->env_start;