Subject: Re: BUG: sleeping function called from ras_epow_interrupt context

From: Thomas Huth <[email-masked]>
Date: Wed, 15 Jul 2015 16:35:02 +0200

On 07/14/2015 11:22 PM, Benjamin Herrenschmidt wrote:
> On Tue, 2015-07-14 at 20:43 +0200, Thomas Huth wrote:
>> Any suggestions how to fix this? Simply revert 587f83e8dd50d? Use
>> mdelay() instead of msleep() in rtas_busy_delay()? Something more
>> fancy?
> 
> A proper fix would be more fancy, the get_sensor should happen in a
> kernel thread instead.

I'm not very familiar with this stuff, but isn't the EPOW interrupt
something that is very time-critical? Moving parts of the handler into a
kernel thread then does not sound like a very good idea to me...

Another question: Can it happen at all that this get-sensor call results
in a sleep condition? Looking at commit ID
81b73dd92b97423b8f5324a59044da478c04f4c4 ("Fix might-sleep warning on
removing cpus"), which apparently fixed a similar issue for CPU
hot-plugging, indicates that at least some of the rtas calls are never
returning the busy code? In that case we could fix this by introducing a
similar rtas_get_sensor_fast() function? (or simply revert 587f83e8dd50d
which would be quite similar, I think)

 Thomas