linux-kernel - Re: [RFC,PATCH 1/2] Add a common struct 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: <20100614064028.GA12159@pengutronix.de>
Date:	Mon, 14 Jun 2010 08:40:28 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Lothar Waßmann <LW@...O-electronics.de>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jeremy Kerr <jeremy.kerr@...onical.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Ben Dooks <ben-linux@...ff.org>
Subject: Re: [RFC,PATCH 1/2] Add a common struct clk

Hello Lothar,

On Mon, Jun 14, 2010 at 08:39:21AM +0200, Lothar Waßmann wrote:
> Hi,
> 
> Benjamin Herrenschmidt writes:
> > On Fri, 2010-06-11 at 12:08 +0200, Lothar Waßmann wrote:
> > > Hi,
> > > 
> > > > > > > Using a mutex in clk_enable()/clk_disable() is a bad idea, since that
> > > > > > > makes it impossible to call those functions in interrupt context.
> > > > IMHO if a device generates an irq its clock should already be on.  This
> > > > way you don't need to enable or disable a clock in irq context.
> > > >  
> > > You may want to disable a clock in the IRQ handler. The VPU driver in
> > > the Freescale BSP for i.MX51 does exactly this.
> > > Anyway I don't see any reason for using a mutex here instead of
> > > spin_lock_irq_save() as all other implementations do.
> > 
> > Because you suddenly make it impossible to sleep inside enable/disable
>               ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> ???
> All implementations so far use spin_lock_irq_save()!
> 
> How would you be able to sleep with a mutex held?
> If you hold a lock you must not sleep, no matter what sort of lock it
> is.
That's wrong.  With a mutex hold you may sleep.

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/