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From: David Brownell <david-b@pacbell.net>
To: David Newall <davidn@davidnewall.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
	Alan Stern <stern@rowland.harvard.edu>,
	linux-pm@lists.linux-foundation.org,
	Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [linux-pm] Fundamental flaw in system suspend, exposed by freezer removal
Date: Tue, 26 Feb 2008 01:16:17 -0800	[thread overview]
Message-ID: <200802260116.18142.david-b@pacbell.net> (raw)
In-Reply-To: <47C3CD15.1060908@davidnewall.com>

On Tuesday 26 February 2008, David Newall wrote:
> 
> Hardware can be inserted and removed while we're in a suspend state; and
> there's nothing that we can do about it until we resume.  Is it fair to
> say, then, that having started suspend, we could reasonably ignore any
> device insertion and removal, and handle it on resume?

"Ignore" seems a bit strong; those events may be wakeup triggers,
which would cause the hardware to make it a very short suspend state.

"Defer handling" is more to the point, be it by hardware or software.


> Presumably we need to scan for hardware changes on resume.

Not on most busses I work with; the hardware issues notifications
whenever the devices are removable.

Which is a Good Thing ... scanning, as you suggest, is inherently
not reliable.  If a mouse is swapped, it likely doesn't matter a
lot whether it's the "same" or not.

But ... how about if some removable storage media was taken out,
updated on a different system, then restored before the resume?
Not many filesystems handle that sanely.  You *really* want to
have hardware which reports disconnect/reconnect events, or which
physically prevents them (locked case etc).

- Dave




  reply	other threads:[~2008-02-26  9:17 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-25 15:39 Alan Stern
2008-02-25 19:46 ` [linux-pm] " Alan Stern
2008-02-25 22:25   ` Rafael J. Wysocki
2008-02-25 23:37     ` Alan Stern
2008-02-26  0:07       ` Rafael J. Wysocki
2008-02-26 15:49         ` Alan Stern
2008-02-26 23:17           ` Rafael J. Wysocki
2008-02-27 16:03             ` Alan Stern
2008-02-27 19:50               ` Rafael J. Wysocki
2008-02-27 20:15                 ` Alan Stern
2008-02-28 22:49                 ` Alan Stern
2008-02-29  0:01                   ` Rafael J. Wysocki
2008-02-29 14:26                   ` Rafael J. Wysocki
2008-02-29 15:53                     ` Alan Stern
2008-02-29 17:02                       ` Rafael J. Wysocki
2008-02-29 18:42                         ` Alan Stern
2008-02-29 21:57                           ` Rafael J. Wysocki
2008-02-29 22:46                             ` Alan Stern
2008-03-01  0:13                               ` Rafael J. Wysocki
2008-03-01 15:30                                 ` Alan Stern
2008-03-02 13:37                                   ` Rafael J. Wysocki
2008-03-02 16:22                                     ` Alan Stern
2008-03-02 19:11                                       ` Rafael J. Wysocki
2008-03-03  3:54                                         ` Alan Stern
2008-03-03 16:32                                           ` Rafael J. Wysocki
2008-03-03 17:43                                             ` Alan Stern
2008-03-03 20:47                                               ` Rafael J. Wysocki
2008-03-03 22:48                                                 ` Alan Stern
2008-03-03 22:56                                                   ` Rafael J. Wysocki
2008-03-03 23:12                                                     ` Alan Stern
2008-03-03 23:18                                                       ` Rafael J. Wysocki
2008-02-26  7:13     ` David Brownell
2008-02-26  8:25       ` David Newall
2008-02-26  9:16         ` David Brownell [this message]
2008-02-26 13:36           ` David Newall
2008-02-26 15:58             ` Alan Stern
2008-02-25 22:24 ` Rafael J. Wysocki
2008-02-27 20:36 ` Benjamin Herrenschmidt

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