linux-kernel - Re: Locking in the clk API, part 2: clk_prepare/clk

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: <20110201152820.GQ31216@n2100.arm.linux.org.uk>
Date:	Tue, 1 Feb 2011 15:28:20 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Jassi Brar <jassisinghbrar@...il.com>,
	Jeremy Kerr <jeremy.kerr@...onical.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	linux-sh@...r.kernel.org,
	Ben Herrenschmidt <benh@...nel.crashing.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Paul Mundt <lethal@...ux-sh.org>, linux-kernel@...r.kernel.org,
	Dima Zavin <dmitriyz@...gle.com>,
	Saravana Kannan <skannan@...eaurora.org>,
	Ben Dooks <ben-linux@...ff.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: Locking in the clk API, part 2: clk_prepare/clk_unprepare

On Tue, Feb 01, 2011 at 04:22:03PM +0100, Uwe Kleine-König wrote:
> Full ack.  (I wonder if you misunderstood me or wanted to put my
> statement into more words.  Jassi didn't like that a clk_enable without
> a previous clk_prepare worked on some platforms and on others it
> doesn't.  With BUG_ON(clk->ops->prepare && !clk->prepare_count) in
> clk_enable we have exactly this situation.)

Even with a NULL clk->ops->prepare function, we still want drivers to
have called clk_prepare().  So we can do something like:

	if (WARN_ON(clk->prepare_count == 0))
		return -EINVAL;

in clk_enable() should be sufficient and noisy enough not to be missed.

I'd avoid BUG_ON() here as that will take the system down, which may
increase the chances of getting useful bug reports.
--
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/