Re: [patch 2.6.13] i386: Ignore masked FPU exceptions

[Ondrej Zary <linux@rainbow-software.org>]

Chuck Ebbert wrote:
> I think ignoring masked FPU exceptions on i386 is the right thing to do.
> Although there is no documentation available for Cyrix MII, I did find
> erratum F-7 for Winchip C6, "FPU instruction may result in spurious
> exception under certain conditions" which seems to indicate that this can
> happen.
>
> Ondrej, this patch on top of 2.6.13 should fix your Cyrix problems.
> Can you confirm?  There was another bug which was already fixed,
> so this should be all that's needed now.

Thanks, it seems to work fine:

rainbow@pentium:~$ ./mprime
             Main Menu

         1.  Test/Primenet
         2.  Test/User Information
         3.  Test/Vacation or Holiday
         4.  Test/Status
         5.  Test/Continue
         6.  Test/Exit
         7.  Advanced/Test
         8.  Advanced/Time
         9.  Advanced/P-1
        10.  Advanced/ECM
        11.  Advanced/Priority
        12.  Advanced/Manual Communication
        13.  Advanced/Unreserve Exponent
        14.  Advanced/Quit Gimps
        15.  Options/CPU
        16.  Options/Preferences
        17.  Options/Torture Test
        18.  Options/Benchmark
        19.  Help/About
        20.  Help/About PrimeNet Server
Your choice: 17

Beginning a continuous self-test to check your computer.
Please read stress.txt.  Hit ^C to end this test.
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Torture Test ran 6 hours, 6 minutes - 0 errors, 0 warnings.


> Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
>
>  arch/i386/kernel/traps.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
>
> --- 2.6.13a.orig/arch/i386/kernel/traps.c
> +++ 2.6.13a/arch/i386/kernel/traps.c
> @@ -804,8 +804,9 @@ void math_error(void __user *eip)
>  	cwd = get_fpu_cwd(task);
>  	swd = get_fpu_swd(task);
>  	switch (swd & ~cwd & 0x3f) {
> -		case 0x000:
> -		default:
> +		case 0x000: /* No unmasked exception */
> +			return;
> +		default:    /* Multiple exceptions */
>  			break;
>  		case 0x001: /* Invalid Op */
>  			/*
> __
> Chuck


--
Ondrej Zary
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