On Sun, 2008-03-16 at 23:27 -0500, Anton Blanchard wrote:
> Since the PMU is an NMI now, it can come at any time we are only soft
> disabled. We must hard disable around the two places we allow the kernel
> stack SLB and r1 to go out of sync. Otherwise the PMU exception can
> force a kernel stack SLB into another slot.
>
> Signed-off-by: Anton Blanchard <[EMAIL PROTECTED]>
Acked-by: Benjamin Herrenschmidt <[EMAIL PROTECTED]>
---
> ---
>
> Index: kernel/arch/powerpc/mm/slb.c
> ===================================================================
> --- kernel.orig/arch/powerpc/mm/slb.c 2007-11-05 11:22:03.000000000 -0600
> +++ kernel/arch/powerpc/mm/slb.c 2007-11-05 18:09:45.000000000 -0600
> @@ -113,6 +113,12 @@ void slb_flush_and_rebolt(void)
> slb_shadow_update(get_paca()->kstack, lflags, 2);
> }
>
> + /*
> + * We can't take a PMU exception in the following code, so hard
> + * disable interrupts.
> + */
> + hard_irq_disable();
> +
> /* We need to do this all in asm, so we're sure we don't touch
> * the stack between the slbia and rebolting it. */
> asm volatile("isync\n"
> Index: kernel/arch/powerpc/kernel/process.c
> ===================================================================
> --- kernel.orig/arch/powerpc/kernel/process.c 2007-11-05 18:10:44.000000000
> -0600
> +++ kernel/arch/powerpc/kernel/process.c 2007-11-05 18:10:46.000000000
> -0600
> @@ -331,6 +331,12 @@ struct task_struct *__switch_to(struct t
> account_process_vtime(current);
> calculate_steal_time();
>
> + /*
> + * We can't take a PMU exception inside _switch() since there is a
> + * window where the kernel stack SLB and the kernel stack are out
> + * of sync. Hard disable here.
> + */
> + hard_irq_disable();
> last = _switch(old_thread, new_thread);
>
> local_irq_restore(flags);
>
>
> _______________________________________________
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> Linuxppc-dev@ozlabs.org
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