Warning at kernel/mutex.c

[u.kleine-koenig@pengutronix.de (Uwe Kleine-König)]

On Tue, Oct 18, 2011 at 06:37:44PM +0100, Russell King - ARM Linux wrote:
> On Tue, Oct 18, 2011 at 02:43:27PM -0200, Fabio Estevam wrote:
> > Hi,
> > 
> > I am running 3.1-rc10 kernel built with mxs_defconfig on a MX28EVK
> > board and I am getting the following:
> > 
> > [    0.200000] Switching to clocksource mxs_timer
> > [    0.220000] Switched to NOHz mode on CPU #0
> > [    0.220000] ------------[ cut here ]------------
> > [    0.220000] WARNING: at kernel/mutex.c:198 mutex_lock_nested+0x260/0x29c()
> > [    0.220000] Modules linked in:
> > [    0.220000] [<c0014478>] (unwind_backtrace+0x0/0xf4) from
> > [<c002630c>] (warn_slowpath_common+0x4c/0x64)
> > [    0.220000] [<c002630c>] (warn_slowpath_common+0x4c/0x64) from
> > [<c0026340>] (warn_slowpath_null+0x1c/0x24)
> > [    0.220000] [<c0026340>] (warn_slowpath_null+0x1c/0x24) from
> > [<c02957cc>] (mutex_lock_nested+0x260/0x29c)
> > [    0.220000] [<c02957cc>] (mutex_lock_nested+0x260/0x29c) from
> > [<c0018580>] (clk_enable+0x2c/0x4c)
> > [    0.220000] [<c0018580>] (clk_enable+0x2c/0x4c) from [<c01cd9e0>]
> > (pl011_console_write+0x20/0x78)
> 
> clk_enable() shouldn't be taking a mutex because drivers can _and_ do
> call it from non-schedulable contexts.  Unfortunately, some clk_enable
> implementations do use a mutex.
> 
> We have a transition path for this, discussed quite a while ago -
> introducing clk_prepare() to do the slow bits of enabling a clock,
> leaving clk_enable() for the fast stuff.
> 
And some time ago I posted a work-around with the obvious downside of
having the clock on longer than necessary. You can find it at

	http://mid.gmane.org/1293117682-18505-1-git-send-email-u.kleine-koenig at pengutronix.de

Best regards
Uwe

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