linux-kernel - Re: [linux-pm] [PATCH] Remove process freezer from suspend to RAM pathway

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Date:	Wed, 4 Jul 2007 16:41:58 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	paulus@...ba.org, mjg59@...f.ucam.org,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [linux-pm] [PATCH] Remove process freezer from suspend to RAM pathway

On Wednesday, 4 July 2007 13:51, Miklos Szeredi wrote:
> > Still, my position is this:
> > 
> > 1) The freezer (in the modified form, with the freezing of kernel threads
> > limited to the ones that want to be frozen) is needed for hibernation.
> > 
> > 2) The freezer is generally not needed for suspend, _but_ there are drivers
> > in the tree that rely on it being used.  Thus, at some point in time we can
> > remove the freezer from the suspend code path, _but_ no sooner than we are
> > sure that the majority of drivers is prepared for that.
> 
> And we won't know if drivers are OK until we remove the freezer,
> catch-22.

I disagree.  We can learn that by auditing the drivers.

> So I think we need to disable the freezer at least in -mm and/or
> optionally in -linus.
> 
> I applied Matthew's patch, and suspend did in fact stop working
> (thinkpad t60), but there was nothing catastrophic.  Here's the dmesg
> if somebody is interested:
> 
> Suspending console(s)
> usb_endpoint usbdev5.3_ep83: PM: suspend 0->2, parent 5-2:1.0 already 2
> usb_endpoint usbdev5.3_ep02: PM: suspend 0->2, parent 5-2:1.0 already 2
> usb_endpoint usbdev5.3_ep81: PM: suspend 0->2, parent 5-2:1.0 already 2
> hub 2-0:1.0: suspend error -16
> suspend_device(): usb_suspend+0x0/0x1c() returns -16
> Could not suspend device usb2: error -16
> usb_endpoint usbdev5.3_ep81: PM: resume from 0, parent 5-2:1.0 still 2
> usb_endpoint usbdev5.3_ep02: PM: resume from 0, parent 5-2:1.0 still 2
> usb_endpoint usbdev5.3_ep83: PM: resume from 0, parent 5-2:1.0 still 2
> Some devices failed to suspend

No, it's not catastrophic, but something like this will result in a bug report
with "regression" in the subject.

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth
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