From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: cpufreq + PREEMPT_RT_FULL give bad context sleeping BUG
Date: Tue, 26 Mar 2013 22:38:02 +0100 (CET)
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References: <alpine.LFD.2.02.1303222301010.22263@ionos> <20130323013003.GU11538@uudg.org> <514DE3BF.5010800@gentil.com> <20130326205107.GB14220@linutronix.de> <alpine.LFD.2.02.1303262203560.22263@ionos> <20130326213356.GC14220@linutronix.de>
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Cc: Linus Walleij <linus.walleij@linaro.org>,
	Santosh Shilimkar <santosh.shilimkar@ti.com>,
	Rob Herring <rob.herring@calxeda.com>,
	linux-rt-users <linux-rt-users@vger.kernel.org>,
	Gregoire Gentil <gregoire@gentil.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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On Tue, 26 Mar 2013, Sebastian Andrzej Siewior wrote:

> * Thomas Gleixner | 2013-03-26 22:07:45 [+0100]:
> 
> >> that means it should trigger on mainline as well.
> >
> >No. It won't. Mainline uses a spinlock which gets converted to a
> >sleeping spinlock on rt.
> >
> >  (rt_spin_lock+0x30/0x64) from (clk_get_rate+0x30/0x54)
> 
> This is true but this spinlock in only available in the OOT code
> Gregoire Gentil pointed out ([0]). In mainline we have a mutex in
> drivers/clk/clk.c and this is what my omap4 blaze is using.
> 
> [0] http://dev.omapzoom.org/?p=integration/kernel-ubuntu.git;a=blob;f=arch/arm/plat-omap/clock.c;h=8c0e8fe2c5c51673e41e4304194d922dbfaedf38;hb=3e1c9f139425663ceee48f92e8d3f23158580334

Yeah, it's that way in mainline as well. I did not look at the source,
I just looked at the backtrace.

So either way, this needs to be resolved :)

Thanks,

	tglx