linux-kernel - Re: [PATCH]: In kernel hibernation, suspend to both

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Message-Id: <201205151942.36335.rjw@sisk.pl>
Date:	Tue, 15 May 2012 19:42:36 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	Bojan Smojver <bojan@...ursive.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	bp@...en8.de
Subject: Re: [PATCH]: In kernel hibernation, suspend to both

On Tuesday, May 15, 2012, Srivatsa S. Bhat wrote:
> On 05/15/2012 05:29 AM, Bojan Smojver wrote:
> 
> > On Mon, 2012-05-14 at 21:47 +1000, Bojan Smojver wrote:
> >> No. That hangs my box.
> >>
> >> This triggers a bug in workqueues code (essentially the same as the
> >> previous patch, except for sys_sync() not being done):
> > 
> > Alan/Srivatsa,
> > 
> > Coming back to the explanation of how this whole thing works, it would
> > seem that at the point of image writing all devices are fully functional
> > (not just some, as I mistakenly believed). However, the processes are
> > supposed to be already frozen, right? Calling suspend_prepare(), which
> > will essentially try to freeze the processes and kernel threads, seems
> > like the wrong thing to do.
> > 
> > Did you guys mean that we should be calling
> > pm_notifier_call_chain(PM_SUSPEND_PREPARE) only here?
> > 
> 
> 
> Exactly! And also arrange for the corresponding PM_POST_SUSPEND notification
> to happen at the end of suspend-to-ram stage...

Actually, no.  The notifiers are supposed to be called when user space is
available, otherwise some things will break badly (firmware loading for
one example IIRC).

So, I think we should pretend that this is all hibernation and, even if
the suspend to RAM phase succeeds, run PM_POST_HIBERNATION notifiers (which
I suppose is what the first Bojan's patch did, right?).

Thanks,
Rafael
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