From: Florian Mickler <florian@mickler.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
"Linux-pm mailing list" <linux-pm@lists.linux-foundation.org>,
"Matthew Garrett" <mjg59@srcf.ucam.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Dmitry Torokhov" <dmitry.torokhov@gmail.com>,
"Arve Hjønnevåg" <arve@android.com>, "Neil Brown" <neilb@suse.de>,
"mark gross" <640e9920@gmail.com>
Subject: Re: [RFC][PATCH] PM: Avoid losing wakeup events during suspend
Date: Mon, 21 Jun 2010 22:40:23 +0200 [thread overview]
Message-ID: <20100621224023.0b14cde7@schatten.dmk.lab> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1006211244140.1687-100000@iolanthe.rowland.org>
On Mon, 21 Jun 2010 12:54:44 -0400 (EDT)
Alan Stern <stern@rowland.harvard.edu> wrote:
> On Mon, 21 Jun 2010, Florian Mickler wrote:
>
> > > > > What happens if an event arrives just before you read
> > > > > /sys/power/wakeup_count, but the userspace consumer doesn't realize
> > > > > there is a new unprocessed event until after the power manager checks
> > > > > it?
> > >
> > > > I think this is not the kernel's problem. In this approach the kernel makes it
> > > > possible for the user space to avoid the race. Whether or not the user space
> > > > will use this opportunity is a different matter.
> > >
> > > It is _not_ possible for userspace to avoid this race. Help from the
> > > kernel is needed.
> >
> > It is possible if every (relevant) userspace program implements a
> > callback for the powermanager to check if one of it's wakeup-sources
> > got activated.
> >
> > That way the powermanager would read /sys/power/wakeup_count, then do
> > the roundtrip to all it's registered users and only then suspend.
>
> After further thought, there's still a race:
Ah, yes. That's what I meant in my other mail with 'how to determine
that an wake event is in flight'.
Read this too late.
> Alan Stern
Cheers,
Flo
next prev parent reply other threads:[~2010-06-21 20:41 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-19 22:05 [RFC][PATCH] PM: Avoid losing wakeup events during suspend Rafael J. Wysocki
2010-06-20 5:52 ` mark gross
2010-06-20 12:49 ` Rafael J. Wysocki
2010-06-20 23:13 ` mark gross
2010-06-20 16:28 ` Alan Stern
2010-06-20 21:50 ` Rafael J. Wysocki
2010-06-21 2:23 ` Alan Stern
2010-06-21 5:32 ` Florian Mickler
2010-06-21 15:23 ` Alan Stern
2010-06-21 20:38 ` Florian Mickler
2010-06-21 22:18 ` Alan Stern
2010-06-21 22:40 ` Rafael J. Wysocki
2010-06-21 22:48 ` Rafael J. Wysocki
2010-06-22 0:50 ` Arve Hjønnevåg
2010-06-22 10:21 ` Rafael J. Wysocki
2010-06-22 14:35 ` Alan Stern
2010-06-22 15:35 ` Rafael J. Wysocki
2010-06-22 19:55 ` Alan Stern
2010-06-22 20:58 ` Rafael J. Wysocki
2010-06-22 19:59 ` [update] " Rafael J. Wysocki
2010-06-22 20:34 ` Alan Stern
2010-06-22 21:41 ` Rafael J. Wysocki
2010-06-23 2:12 ` Alan Stern
2010-06-23 10:09 ` Rafael J. Wysocki
2010-06-23 15:21 ` Alan Stern
2010-06-23 22:17 ` Rafael J. Wysocki
2010-06-24 13:13 ` [update 2] " Rafael J. Wysocki
2010-06-24 15:06 ` Rafael J. Wysocki
2010-06-24 15:35 ` Alan Stern
2010-06-24 23:00 ` [update 3] " Rafael J. Wysocki
2010-06-25 14:42 ` Alan Stern
2010-06-25 20:33 ` Rafael J. Wysocki
2010-06-24 15:44 ` [update 2] " Alan Stern
2010-06-24 16:19 ` Rafael J. Wysocki
2010-06-24 17:09 ` Alan Stern
2010-06-24 23:06 ` Rafael J. Wysocki
2010-06-25 15:09 ` Alan Stern
2010-06-25 20:37 ` Rafael J. Wysocki
2010-06-25 20:57 ` Alan Stern
2010-06-25 6:40 ` Florian Mickler
2010-06-25 13:28 ` Rafael J. Wysocki
[not found] ` <201006222159.28081.rjw__37084.1419128284$1277237903$gmane$org@sisk.pl>
2010-06-24 14:16 ` [update] " Andy Lutomirski
2010-06-24 14:45 ` Alan Stern
2010-06-24 14:48 ` Rafael J. Wysocki
2010-06-24 15:21 ` Andy Lutomirski
2010-06-22 23:00 ` mark gross
2010-06-21 16:54 ` Alan Stern
2010-06-21 20:40 ` Florian Mickler [this message]
2010-06-21 21:18 ` Rafael J. Wysocki
2010-06-21 22:27 ` Alan Stern
2010-06-21 6:13 ` mark gross
2010-06-21 12:10 ` tytso
2010-06-21 12:22 ` Alan Cox
2010-06-21 12:26 ` Florian Mickler
2010-06-21 13:42 ` tytso
2010-06-21 14:01 ` Alan Cox
2010-06-22 1:07 ` mark gross
2010-06-21 16:01 ` Alan Stern
2010-06-22 1:25 ` mark gross
2010-06-22 2:24 ` Alan Stern
2010-06-21 21:58 ` Rafael J. Wysocki
2010-06-20 22:58 ` mark gross
2010-06-21 2:33 ` Alan Stern
2010-06-21 4:04 ` [linux-pm] " David Brownell
2010-06-21 6:02 ` David Brownell
2010-06-21 15:06 ` Alan Stern
2010-06-21 5:55 ` mark gross
2010-06-21 12:39 ` Florian Mickler
2010-06-21 15:57 ` Alan Stern
2010-06-22 1:58 ` mark gross
2010-06-22 2:46 ` Alan Stern
2010-06-22 9:24 ` Rafael J. Wysocki
2010-06-22 6:18 ` Florian Mickler
2010-06-22 23:22 ` mark gross
2010-06-22 9:29 ` Rafael J. Wysocki
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