[PATCH-V2 1/1] sparc: Fix context switch on SMP

[Daniel Cederman]

Ok, then I will remove that line. I like the assert idea and will add 
that to the patch. Thank you for your comments and help!

On 2015-11-16 13:52, Sebastian Huber wrote:
> On 16/11/15 13:14, Daniel Cederman wrote:
>> I was unsure if the ET bit was always set or not for newly created
>> task contexts, or if this was the first place that traps got enabled
>> for a new task. If it is always set we can remove that instruction.
>
> The PSR is initialized like this (_CPU_Context_Initialize()):
>
> [...]
>      /*
>       *  Build the PSR for the task.  Most everything can be 0 and the
>       *  CWP is corrected during the context switch.
>       *
>       *  The EF bit determines if the floating point unit is available.
>       *  The FPU is ONLY enabled if the context is associated with an FP
> task
>       *  and this SPARC model has an FPU.
>       */
>
>      sparc_get_psr( tmp_psr );
>      tmp_psr &= ~SPARC_PSR_PIL_MASK;
>      tmp_psr |= (new_level << 8) & SPARC_PSR_PIL_MASK;
>      tmp_psr &= ~SPARC_PSR_EF_MASK;      /* disabled by default */
>
> #if (SPARC_HAS_FPU == 1)
>      /*
>       *  If this bit is not set, then a task gets a fault when it accesses
>       *  a floating point register.  This is a nice way to detect floating
>       *  point tasks which are not currently declared as such.
>       */
>
>      if ( is_fp )
>        tmp_psr |= SPARC_PSR_EF_MASK;
> #endif
>      the_context->psr = tmp_psr;
> [...]
>
> Since traps must be enabled at C level, this should be fine.
>
> Maybe add this to the patch for documentation purposes:
>
> diff --git a/cpukit/score/cpu/sparc/cpu.c b/cpukit/score/cpu/sparc/cpu.c
> index 569b6f8..5434355 100644
> --- a/cpukit/score/cpu/sparc/cpu.c
> +++ b/cpukit/score/cpu/sparc/cpu.c
> @@ -356,6 +356,9 @@ void _CPU_Context_Initialize(
>       tmp_psr |= (new_level << 8) & SPARC_PSR_PIL_MASK;
>       tmp_psr &= ~SPARC_PSR_EF_MASK;      /* disabled by default */
>
> +    /* _CPU_Context_restore_heir() relies on this */
> +    _Assert( ( tmp_psr & SPARC_PSR_ET_MASK ) != 0 );
> +
>   #if (SPARC_HAS_FPU == 1)
>       /*
>        *  If this bit is not set, then a task gets a fault when it accesse
>

-- 
Daniel Cederman
Software Engineer
Cobham Gaisler