From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Todd Poynor <tpoynor@mvista.com>,
Patrick Mochel <mochel@digitalimplant.org>,
linux-hotplug-devel@lists.sourceforge.net,
Linux Kernel list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Hotplug for device power state changes
Date: Fri, 30 Apr 2004 08:30:12 +0000 [thread overview]
Message-ID: <20040430093012.A30928@flint.arm.linux.org.uk> (raw)
In-Reply-To: <1083286226.20473.159.camel@gaston>; from benh@kernel.crashing.org on Fri, Apr 30, 2004 at 10:50:26AM +1000
On Fri, Apr 30, 2004 at 10:50:26AM +1000, Benjamin Herrenschmidt wrote:
> This is dangerous.
>
> If the device you are suspending is on the VM path in any way,
> beeing synchronous with a userland call can deadlock you solid.
And not being synchronous means that there's no point in calling
userland, because userland won't run before the machine has
suspended, so there's no point in calling it in the first place.
Also consider the case where you suspend, and asynchronously queue
up all these suspend scripts to run. Then you resume and queue up
the resume scripts to run. What order do the suspend and resume
scripts ultimately end up being run?
What if the scripts have side effects like releasing and re-acquiring
your DHCP allocation - what would be the effect of the suspend script
completing after the resume script?
What about the case where suspend/resume scripts bring up/tear down
any communication protocol?
Maybe we should have a two-pass approach, where the first pass
synchronously tells userspace about the suspend, and the second
pass does the actual suspend. Then for resume the opposite.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/
2.6 Serial core
-------------------------------------------------------
This SF.Net email is sponsored by: Oracle 10g
Get certified on the hottest thing ever to hit the market... Oracle 10g.
Take an Oracle 10g class now, and we'll give you the exam FREE.
http://ads.osdn.com/?ad_id149&alloc_idÅ66&op=click
_______________________________________________
Linux-hotplug-devel mailing list http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel
next prev parent reply other threads:[~2004-04-30 8:30 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20040429202654.GA9971@dhcp193.mvista.com>
2004-04-29 21:42 ` [PATCH] Hotplug for device power state changes Russell King
2004-04-29 22:36 ` Todd Poynor
2004-04-30 0:50 ` Benjamin Herrenschmidt
2004-04-30 8:30 ` Russell King [this message]
2004-04-30 19:59 ` Todd Poynor
2004-04-30 21:56 ` Greg KH
2004-05-01 1:16 ` Todd Poynor
2004-05-01 1:48 ` Greg KH
2004-05-03 21:33 ` Todd Poynor
2004-05-01 0:03 ` Nigel Cunningham
2004-05-03 22:04 ` Todd Poynor
2004-04-30 19:07 ` Todd Poynor
2004-05-15 1:40 ` Nicolas Pitre
2004-05-15 23:34 ` Pavel Machek
[not found] ` <Pine.LNX.4.50.0405040819490.3562-100000@monsoon.he.net>
2004-05-04 20:36 ` Todd Poynor
[not found] ` <Pine.LNX.4.50.0405042110440.30304-100000@monsoon.he.net>
2004-05-06 1:08 ` Todd Poynor
2004-05-14 2:50 ` Pavel Machek
2004-05-15 2:08 ` Todd Poynor
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20040430093012.A30928@flint.arm.linux.org.uk \
--to=rmk+lkml@arm.linux.org.uk \
--cc=benh@kernel.crashing.org \
--cc=linux-hotplug-devel@lists.sourceforge.net \
--cc=linux-kernel@vger.kernel.org \
--cc=mochel@digitalimplant.org \
--cc=tpoynor@mvista.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).