From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx109.postini.com [74.125.245.109]) by kanga.kvack.org (Postfix) with SMTP id 9B16E6B0032 for ; Fri, 30 Aug 2013 20:36:44 -0400 (EDT) Message-ID: <1377909312.10300.908.camel@misato.fc.hp.com> Subject: Re: [PATCH 3/3] PM / hibernate / memory hotplug: Rework mutual exclusion From: Toshi Kani Date: Fri, 30 Aug 2013 18:35:12 -0600 In-Reply-To: <1984629.rbRksDyNff@vostro.rjw.lan> References: <9589253.Co8jZpnWdd@vostro.rjw.lan> <1562298.ZjRvhqQzT7@vostro.rjw.lan> <1377908599.10300.901.camel@misato.fc.hp.com> <1984629.rbRksDyNff@vostro.rjw.lan> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Rafael J. Wysocki" Cc: ACPI Devel Maling List , LKML , Linux PM list , Yasuaki Ishimatsu , linux-mm@kvack.org On Sat, 2013-08-31 at 02:39 +0200, Rafael J. Wysocki wrote: > On Friday, August 30, 2013 06:23:19 PM Toshi Kani wrote: > > On Thu, 2013-08-29 at 23:18 +0200, Rafael J. Wysocki wrote: > > > From: Rafael J. Wysocki > > > > > > Since all of the memory hotplug operations have to be carried out > > > under device_hotplug_lock, they won't need to acquire pm_mutex if > > > device_hotplug_lock is held around hibernation. > > > > > > For this reason, make the hibernation code acquire > > > device_hotplug_lock after freezing user space processes and > > > release it before thawing them. At the same tim drop the > > > lock_system_sleep() and unlock_system_sleep() calls from > > > lock_memory_hotplug() and unlock_memory_hotplug(), respectively. > > > > > > Signed-off-by: Rafael J. Wysocki > > > --- > > > kernel/power/hibernate.c | 4 ++++ > > > kernel/power/user.c | 2 ++ > > > mm/memory_hotplug.c | 4 ---- > > > 3 files changed, 6 insertions(+), 4 deletions(-) > > > > > > Index: linux-pm/kernel/power/hibernate.c > > > =================================================================== > > > --- linux-pm.orig/kernel/power/hibernate.c > > > +++ linux-pm/kernel/power/hibernate.c > > > @@ -652,6 +652,7 @@ int hibernate(void) > > > if (error) > > > goto Exit; > > > > > > + lock_device_hotplug(); > > > > Since hibernate() can be called from sysfs, do you think the tool may > > see this as a circular dependency with p_active again? This shouldn't > > be a problem in practice, though. > > /sys/power/state isn't a device attribute even and is never removed, so it > would be very sad and disappointing if lockdep reported that as a circular > dependency. The deadlock is surely not possible here anyway. Agreed. The code looks good otherwise, and this is a nice cleanup. If it is OK to ignore the possible warning from the tool (which I do not know the rule here), feel free to add my ack to patch 2/3 and 3/3 as well. Thanks, -Toshi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org