linux-kernel - Re: Locking in the clk API

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: <20110111105609.GO24920@pengutronix.de>
Date:	Tue, 11 Jan 2011 11:56:09 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Jeremy Kerr <jeremy.kerr@...onical.com>, linux-sh@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Ben Herrenschmidt <benh@...nel.crashing.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: Locking in the clk API

Hello Russell,

On Tue, Jan 11, 2011 at 10:47:09AM +0000, Russell King - ARM Linux wrote:
> On Tue, Jan 11, 2011 at 11:39:29AM +0100, Uwe Kleine-König wrote:
> > A quick look into Digi's BSP (digiEL-5.0) shows they implemented
> > something I suggested earlier here:
> >
> > [...]
> > 
> > 
> > I think the idea is nice.  At least it allows with a single lock to
> > implement both, sleeping and atomic clks without the need to mark the
> > atomicity in a global flag.
> 
> It doesn't.  clk_enable() here can still end up trying to sleep when
> it's called from IRQ context - the code doesn't solve that.  All it
> means is that the intermediate code doesn't care whether clk->endisable
> ends up sleeping or not.
Obviousley you're right and your last sentence is all I intended to
claim.

> What it does do is return -EBUSY if there are two concurrent attempts
> to enable the same clock.  How many drivers today deal sanely with
> such an error from clk_enable(), and how many would just fail their
> probe() call on such an occurance?
Yes, that's the ugly part.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
--
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/