linux-kernel - Re: [RFC][PATCH] PM: Introduce new top level suspend and hibernation callbacks (rev. 3)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Pine.LNX.4.44L0.0803261001080.4755-100000@iolanthe.rowland.org>
Date:	Wed, 26 Mar 2008 10:03:38 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Greg KH <greg@...ah.com>, Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexey Starikovskiy <astarikovskiy@...e.de>,
	David Brownell <david-b@...bell.net>,
	Pavel Machek <pavel@....cz>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [RFC][PATCH] PM: Introduce new top level suspend and hibernation
 callbacks (rev. 3)

On Tue, 25 Mar 2008, Rafael J. Wysocki wrote:

> > I just thought of another problem.  At the point where
> > local_irq_disable() is called, in between device_suspend() and
> > device_power_down(), it is possible in a preemptible kernel that
> > another task is holding dpm_list_mtx and is in the middle of updating
> > the list pointers.  This would mess up the traversal in
> > device_power_down().
> > 
> > I'm not sure about the best way to prevent this.  Is it legal to call
> > unlock_mutex() while interrupts or preemption are disabled?
> 
> Well, I think it is, but I'm not sure how that can help.
> 
> To prevent the race from happening, we can lock dpm_list_mtx before switching
> interrupts off in kernel/power/main.c:suspend_enter() and analogously in
> kernel/power/disk.c .

That's right.  And once interrupts are turned off you should unlock 
dpm_list_mtx again, in case a noirq method wants to unregister a 
device.  Hence my question: Is it legal to call unlock_mutex() while 
interrupts are disabled?

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/