On Mon, Jan 27, 2003 at 10:29:29AM -0800, Jun Sun wrote:
> On Sun, Jan 26, 2003 at 02:58:09AM +0100, Vivien Chappelier wrote:
> > Hi,
> >
> > At various places in the 2.5 kernel, the fpu is accessed in
> > kernel mode with CU1 not set, causing an unexpected exception. This patch
> > makes sure FPU can be accessed by the kernel, though it may only
> > be a workaround. Any comment from someone with a better understanding of
> > the FPU access/context switching code?
> >
> > Vivien.
> >
> > --- include/asm-mips64/fpu.h 2002-12-11 20:44:20.000000000 +0100
> > +++ include/asm-mips64/fpu.h 2002-12-11 21:51:44.000000000 +0100
> > @@ -109,6 +109,7 @@
> >
> > static inline void save_fp(struct task_struct *tsk)
> > {
> > + enable_fpu();
> > if (mips_cpu.options & MIPS_CPU_FPU)
> > _save_fp(tsk);
> > }
> > --- include/asm-mips/fpu.h 2002-12-11 20:44:20.000000000 +0100
> > +++ include/asm-mips/fpu.h 2002-12-11 21:51:44.000000000 +0100
> > @@ -109,6 +109,7 @@
> >
> > static inline void save_fp(struct task_struct *tsk)
> > {
> > + enable_fpu();
> > if (mips_cpu.options & MIPS_CPU_FPU)
> > _save_fp(tsk);
> > }
>
> The above two hunks seem to be right.
>
There are two places which call save_fp(). Just verified that in
both places current process should be fpu owner and therefore
FPU *should* be enabled.
Basically whenever current process is fpu owner, the FPU should be
enabled. Apparently something in 2.5 breaks that fundamental assumption.
Will look into it later.
Jun
