linux-kernel - Re: broken suspend [Was: 2.6.24-rc2-mm1]

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Message-ID: <Pine.LNX.4.44L0.0711182156330.22727-100000@netrider.rowland.org>
Date:	Sun, 18 Nov 2007 22:04:52 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Jiri Slaby <jirislaby@...il.com>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <greg@...ah.com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	<r.marek@...embler.cz>, <lm-sensors@...sensors.org>
Subject: Re: broken suspend [Was: 2.6.24-rc2-mm1]

On Sun, 18 Nov 2007, Jiri Slaby wrote:

> > gives coretemp_cpu_callback -> coretemp_device_remove ->
> > platform_device_unregister, so coretemp seems to be what I have and you don't.

Yes.

For the coretemp developers: coretemp_cpu_callback() needs to be more 
careful about what it does.  During a system sleep transition (suspend, 
hibernate, resume) it isn't possible to register or unregister a 
device.  Attempts to register will fail and attempts to unregister will 
block until the system sleep is over -- and for this callback that 
means hanging.

It's not clear what the best way is to fix this.  Perhaps the CPU 
notification should be sent along with a special flag indicating that 
the CPU transition is part of a system sleep (although this seems 
racy).  Perhaps the driver should notice when a system sleep begins, 
and defer all CPU-change handling until after the sleep is over.

Alan Stern

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