Re: Strange MXCSR messages?

["Thomas E. Spanjaard" <tgen@xxxxxxxxxxxxx>]

Joerg Anslik wrote:
> I enabled "nata" support on one of my boxes lately, and now my
> /var/log/messages gets flooded with entries like this:

Is the problem not encountered if you recompile from the exact same 
sources, but with old ATA instead of NATA?

> [...]
> kernel: pid 54403 (icecast) signal return from user: illegal FP MXCSR
> ffff0010
> last message repeated 24 times
> kernel: pid 9033 (mysqld) signal return from user: illegal FP MXCSR
> ffff0010
> last message repeated 7 times
> [...]
> I also found it's pretty hard to get information about this "MXCSR"
> stuff, so if someone could give me a short explanation...? As far as I
> can tell, it's some kind of register stuff.

MXCSR is the SSE control/status register, and that value means the 
Underflow Flag bit is set. The other 1 bits are reserved ones, which 
should *NOT* be set to 1. Attempting to set them to 1 will result in a 
general protection exception, which is probably what you're seeing here. 
My guess is, the recent changes to how the signal code in the kernel 
saves and restores the MXCSR register, introduced this bug, and not 
NATA. I'll have a look later at the code in question.

Cheers,
--
        Thomas E. Spanjaard
        tgen@netphreax.net

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