Re: Magic Alt-SysRq change in 2.6.18-rc1

From: Chuck Ebbert
Date: Sun Jul 09 2006 - 20:04:44 EST


In-Reply-To: <Pine.LNX.4.44L0.0607091657490.28904-100000@xxxxxxxxxxxxxxxxxxxx>

On Sun, 9 Jul 2006 17:06:57 -0400, Alan Stern wrote:
>
> <...> changes in the behavior of Alt-SysRq?
>
> Before 2.6.18-rc1, I used to be able to use it as follows:
>
> Press and hold an Alt key,
> Press and hold the SysRq key,
> Release the Alt key,
> Press and release some hot key like S or T or 7,
> Repeat the previous step as many times as desired,
> Release the SysRq key.
>
> This scheme doesn't work any more, or if it does, the timing requirements
> are now much stricter. In practice I have to hold down all three keys at
> the same time; I can't release the Alt key before pressing the hot key.


Look at the change history for keyboard.c:


[PATCH] fix magic sysrq on strange keyboards

Magic sysrq fails to work on many keyboards, particulary most of notebook
keyboards. This patch fixes it.

The idea is quite simple: Discard the SysRq break code if Alt is still being
held down. This way the broken keyboard can send the break code (or the user
with a normal keyboard can release the SysRq key) and the kernel waits until
the next key is pressed or the Alt key is released.


--
Chuck
"You can't read a newspaper if you can't read." --George W. Bush
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