On Mon, Aug 20, 2012 at 10:57:34AM +0200, Lothar Wa?mann wrote:

Hi,

Uwe Kleine-K?nig writes:

quoted

Hello,

while triggering a reboot via sysrq on an ARM machine I saw a "BUG:
sleeping function called from invalid context" message (details below).
The reason is that the sysrq handler is calling the restart hook in irq
context. So what should be done about that? The obvious possiblities
are:

 a) ignore the problem as it won't result in problems (and maybe somehow
    silence the warnign); or
 b) make the restart hook atomic; or
 c) assert sysrq not calling the hook in atomic mode

What do you think?

This has been discussed earlier (with your participation) with 'a)'
being the conclusion.
http://lists.infradead.org/pipermail/linux-arm-kernel/2010-December/033877.html

Except if you look at the backtrace, it seems that it fails to restart.
There are two attempts there at making it restart so the first could
not have succeeded.