On Tue, 2024-01-02 at 18:25 +0800, Xi Ruoyao wrote:
> On Tue, 2024-01-02 at 18:17 +0800, Xi Ruoyao wrote:
> > The only other architecture setting FCSR in SET_PERSONALITY2 is MIPS.
> > They do this for supporting different FP flavors (NaN encodings etc).
> > which do not exist on LoongArch. I'm not sure how MIPS evades the issue
> > (or maybe it's just buggy too) but I'll investigate it later.
>
> Phew. I just managed to recommission my 3A4000 and I can reproduce the
> issue as well with Linux 5.18.1 (the latest kernel release when I
> decommissioned it) and CONFIG_PREEMPT=y.
>
> % cat measure.c
> #include <fenv.h>
> int main() { return fetestexcept(FE_INEXACT); }
>
> % echo $((1./3))
> 0.33333333333333331
>
> % while ./a.out; do ; done
> (stopped in seconds)
>
> I'm building the mainline kernel on the 3A4000 now, will see if the
> issue still exists...
Still happening with 6.7.0-rc8. I'm not sure how to fix it for MIPS.
Maybe lose_fpu in SET_PERSONALITY2? But to me doing so will be really
nasty. Anyway I'll leave this for MIPS maintainers.
--
Xi Ruoyao <xry111@xxxxxxxxxxx>
School of Aerospace Science and Technology, Xidian University
