linux-kernel - Re: [patch 128/197] freezer: add try_to

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Message-ID: <4641CAAF.8060103@s5r6.in-berlin.de>
Date:	Wed, 09 May 2007 15:20:47 +0200
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	ego@...ibm.com
CC:	Pavel Machek <pavel@....cz>, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, rjw@...k.pl,
	James.Bottomley@...elEye.com, aneesh.kumar@...il.com,
	drzeus@...eus.cx, dwmw2@...radead.org, greg@...ah.com,
	mingo@...e.hu, neilb@...e.de, oleg@...sign.ru,
	paulmck@...ux.vnet.ibm.com, vatsa@...ibm.com,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 128/197] freezer: add try_to_freeze calls to all kernel
 threads

Gautham R Shenoy wrote:
> freezer_exempt() as of now does what its name says. I.e, exempt the
> thread from all kinds of freeze chills.
> 
> But with more subsystems using the process freezer, the exemption needs
> to be event specific. There may be threads which should not be frozen 
> for say kprobes, should be frozen for cpu-hotplug. This selective
> freezing is not yet available. But it will be soon...

Thanks for the (necessary!) clarification.
Let me point out that the usual process would be to replace

	freezer_exempt(current);
	for (;;) {
		...;
by
	freezer_exempt_for_io(current);
	for (;;) {
		try_to_freeze();
		...;

when or after freezer_exempt_for_io was implemented.

But as it was submitted now, we are temporarily left with

	freezer_exempt(current);
	for (;;) {
		try_to_freeze();  /* useless irritating no-op */
		...;

without any benefit.  (And this explanatory comment ^^^ wasn't even
added; we only have the git log as explanation.)

As subsystem maintainer I have to trust now that "soon" actually means
"soon" and not "RSN"; otherwise my responsibility would be to send a NAK.
-- 
Stefan Richter
-=====-=-=== -=-= -=--=
http://arcgraph.de/sr/
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