From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755398AbZDHIoT (ORCPT ); Wed, 8 Apr 2009 04:44:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752222AbZDHIoC (ORCPT ); Wed, 8 Apr 2009 04:44:02 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:44406 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751711AbZDHIoA convert rfc822-to-8bit (ORCPT ); Wed, 8 Apr 2009 04:44:00 -0400 From: KOSAKI Motohiro To: Neil Brown , Greg Kroah-Hartman , LKML Subject: [PATCH] sysfs poll should keep the poll rule of normal regular file. Cc: kosaki.motohiro@jp.fujitsu.com Message-Id: <20090408173935.8D7E.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 8BIT X-Mailer: Becky! ver. 2.50 [ja] Date: Wed, 8 Apr 2009 17:43:57 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently, following test programs don't finished. % ruby -e ' Thread.new { sleep } File.read("/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies") ' strace expose the reason. ... open("/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies", O_RDONLY|O_LARGEFILE) = 3 ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbf9fa6b8) = -1 ENOTTY (Inappropriate ioctl for device) fstat64(3, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0 _llseek(3, 0, [0], SEEK_CUR) = 0 select(4, [3], NULL, NULL, NULL) = 1 (in [3]) read(3, "1400000 1300000 1200000 1100000 1"..., 4096) = 62 select(4, [3], NULL, NULL, NULL Because Ruby (the scripting language) VM assume select system-call against regular file don't block. (POSIX gurantee it.) But sysfs_poll() don't keep this rule although sysfs file can read and write always. This patch restore proper poll behavior to sysfs. /sys/block/md*/md/sync_action polling application and another sysfs updating sensitive application still can use POLLERR and POLLPRI. Cc: Neil Brown Cc: Greg Kroah-Hartman Signed-off-by: KOSAKI Motohiro -- fs/sysfs/file.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 289c43a..4a302f8 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -446,11 +446,11 @@ static unsigned int sysfs_poll(struct file *filp, poll_table *wait) if (buffer->event != atomic_read(&od->event)) goto trigger; - return 0; + return DEFAULT_POLLMASK; trigger: buffer->needs_read_fill = 1; - return POLLERR|POLLPRI; + return DEFAULT_POLLMASK|POLLERR|POLLPRI; } void sysfs_notify_dirent(struct sysfs_dirent *sd)