linux-kernel - Re: [RFC PATCH 00/13] firmware loader: introduce cache/uncache firmware

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Date:	Wed, 25 Jul 2012 10:23:40 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Borislav Petkov <borislav.petkov@....com>,
	linux-kernel@...r.kernel.org, Matthew Garrett <mjg@...hat.com>,
	linux-usb <linux-usb@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oneukum@...e.de>
Subject: Re: [RFC PATCH 00/13] firmware loader: introduce cache/uncache firmware

On Wed, Jul 25, 2012 at 5:35 AM, Ming Lei <ming.lei@...onical.com> wrote:
>
> The below patch should fix the problem above.

Actually, I think we could make this even simpler.

There's nothing wrong with saying "user mode is enabled" *just* before
we unthaw things, if we also simply guarantee that there is no
sleeping lock or similar that we might get caught on (causing a
deadlock or other untimely waking) before we've actually thawed
everything.

So *if* the only problem wrt the USB hub code comes from this area,
then I think the solution might be as simple as just moving the
"usermodehelper_enable()" up a few lines, with a comment. Something
like the *untested* and whitespace-damaged thing below..

Rafael? Who has one of those isight things and has seen the warning to test?

               Linus

---
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 19db29f67558..5bf50e488196 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -181,6 +181,12 @@ void thaw_processes(void)
        pm_freezing = false;
        pm_nosig_freezing = false;

+       /*
+        * User mode helper are available again (or will be,
+        * modulo scheduling)
+        */
+       usermodehelper_enable();
+
        oom_killer_enable();

        printk("Restarting tasks ... ");
@@ -193,8 +199,6 @@ void thaw_processes(void)
        } while_each_thread(g, p);
        read_unlock(&tasklist_lock);

-       usermodehelper_enable();
-
        schedule();
        printk("done.\n");
 }
--
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