From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751295AbeBTTto (ORCPT ); Tue, 20 Feb 2018 14:49:44 -0500 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:32918 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750732AbeBTTtn (ORCPT ); Tue, 20 Feb 2018 14:49:43 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;CH=green;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07486;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0SyIwpCz_1519156170; From: Yang Shi To: akpm@linux-foundation.org, mingo@kernel.org, adobriyan@gmail.com Cc: yang.shi@linux.alibaba.com, linux-kernel@vger.kernel.org Subject: [PATCH] fs: proc: use down_read_killable in proc_pid_cmdline_read() Date: Wed, 21 Feb 2018 03:49:29 +0800 Message-Id: <1519156169-11883-1-git-send-email-yang.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; -- 1.8.3.1