On Thu, 2009-08-06 at 19:03 +0200, Philippe Gerum wrote:
> On Wed, 2009-08-05 at 17:51 -0400, Andreas Glatz wrote:
> > Hi,
> >
> > I'm running xenomai-2.4.8, Linux-2.6.26 on a MPC8360 PowerPC.
> >
> > I enabled nucleus debugging and found out that tasks sometimes
> > switch to secondary mode due to data alignment exceptions (#1536 ==
> > 0x600):
> >
> > <snip>
> > Xenomai: Switching bgndT30_3 to secondary mode after exception #1536
> > from user-space at 0x101013f4 (pid 3191)
> > Xenomai: Switching bgndT30_3 to secondary mode after exception #1536
> > from user-space at 0x101013f4 (pid 3191)
> > ...
> > </snip>
> >
> > I know that we get those exceptions because we pass the -fpack-struct
> > option to gcc and some data in structures are misaligned. It would
> > be quite a lot of work to go through the code to change it so that
> > we don't have to pass the -fpack-struct option.
> >
> > Is there a way to execute the exception handler from primary mode
> > to prevent the tasks to switch to secondary mode?
>
> I have absolutely no freaking idea whether the following patch will
> work, but you are welcome to feel lucky:
>
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index 701fe3b..3efe546 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -917,7 +917,8 @@ void alignment_exception(struct pt_regs *regs)
> {
> int sig, code, fixed = 0;
>
> - if (ipipe_trap_notify(IPIPE_TRAP_ALIGNMENT,regs))
> + if (test_bit(IPIPE_NOSTACK_FLAG, &ipipe_this_cpudom_var(status)) &&
> + ipipe_trap_notify(IPIPE_TRAP_ALIGNMENT, regs))
> return;
>
> /* we don't implement logging of alignment exceptions */
> @@ -930,6 +931,10 @@ void alignment_exception(struct pt_regs *regs)
> return;
> }
>
> + if (!ipipe_root_domain_p &&
> + ipipe_trap_notify(IPIPE_TRAP_ALIGNMENT, regs))
> + return;
> +
> /* Operand address was bad */
> if (fixed == -EFAULT) {
> sig = SIGSEGV;
>
This one should require a bit less luck to work in some cases:
diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c
index e06f75d..89f9521 100644
--- a/arch/powerpc/kernel/align.c
+++ b/arch/powerpc/kernel/align.c
@@ -788,10 +788,11 @@ int fix_alignment(struct pt_regs *regs)
if (flags & S) {
/* Single-precision FP store requires conversion... */
#ifdef CONFIG_PPC_FPU
- preempt_disable();
+ unsigned long irqflags;
+ ipipe_preempt_disable(irqflags);
enable_kernel_fp();
cvt_df(&data.dd, (float *)&data.v[4], ¤t->thread);
- preempt_enable();
+ ipipe_preempt_enable(irqflags);
#else
return 0;
#endif
@@ -832,10 +833,13 @@ int fix_alignment(struct pt_regs *regs)
/* Single-precision FP load requires conversion... */
case LD+F+S:
#ifdef CONFIG_PPC_FPU
- preempt_disable();
+ {
+ unsigned long irqflags;
+ ipipe_preempt_disable(irqflags);
enable_kernel_fp();
cvt_fd((float *)&data.v[4], &data.dd, ¤t->thread);
- preempt_enable();
+ ipipe_preempt_enable(irqflags);
+ }
#else
return 0;
#endif
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 6979da6..46b0ca1 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -62,6 +62,8 @@ struct task_struct *last_task_used_spe = NULL;
*/
void flush_fp_to_thread(struct task_struct *tsk)
{
+ unsigned long flags;
+
if (tsk->thread.regs) {
/*
* We need to disable preemption here because if we didn't,
@@ -71,7 +73,7 @@ void flush_fp_to_thread(struct task_struct *tsk)
* FPU, and then when we get scheduled again we would store
* bogus values for the remaining FP registers.
*/
- preempt_disable();
+ ipipe_preempt_disable(flags);
if (tsk->thread.regs->msr & MSR_FP) {
#ifdef CONFIG_SMP
/*
@@ -85,13 +87,13 @@ void flush_fp_to_thread(struct task_struct *tsk)
#endif
giveup_fpu(tsk);
}
- preempt_enable();
+ ipipe_preempt_enable(flags);
}
}
void enable_kernel_fp(void)
{
- WARN_ON(preemptible());
+ WARN_ON(ipipe_root_domain_p && preemptible());
#ifdef CONFIG_SMP
if (current->thread.regs && (current->thread.regs->msr & MSR_FP))
@@ -198,15 +200,17 @@ EXPORT_SYMBOL(enable_kernel_spe);
void flush_spe_to_thread(struct task_struct *tsk)
{
+ unsigned long flags;
+
if (tsk->thread.regs) {
- preempt_disable();
+ ipipe_preempt_disable(flags);
if (tsk->thread.regs->msr & MSR_SPE) {
#ifdef CONFIG_SMP
BUG_ON(tsk != current);
#endif
giveup_spe(tsk);
}
- preempt_enable();
+ ipipe_preempt_enable(flags);
}
}
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 701fe3b..3efe546 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -917,7 +917,8 @@ void alignment_exception(struct pt_regs *regs)
{
int sig, code, fixed = 0;
- if (ipipe_trap_notify(IPIPE_TRAP_ALIGNMENT,regs))
+ if (test_bit(IPIPE_NOSTACK_FLAG, &ipipe_this_cpudom_var(status)) &&
+ ipipe_trap_notify(IPIPE_TRAP_ALIGNMENT, regs))
return;
/* we don't implement logging of alignment exceptions */
@@ -930,6 +931,10 @@ void alignment_exception(struct pt_regs *regs)
return;
}
+ if (!ipipe_root_domain_p &&
+ ipipe_trap_notify(IPIPE_TRAP_ALIGNMENT, regs))
+ return;
+
/* Operand address was bad */
if (fixed == -EFAULT) {
sig = SIGSEGV;
--
Philippe.
_______________________________________________
Xenomai-help mailing list
[email protected]
https://mail.gna.org/listinfo/xenomai-help
