[Cbe-oss-dev] No Subject

[Benjamin Herrenschmidt]

On Tue, 2008-02-26 at 06:14 +0100, Arnd Bergmann wrote:
> Subject: spufs: synchronize IRQ when disabling
> 
> There is a small race between the context save procedure
> and the SPU interrupt handling, where we expect all interrupt
> processing to have finished after disabling them, while
> an interrupt is still being processed on another CPU.
> 
> The obvious fix is to call synchronize_irq() after disabling
> the interrupts at the start of the context save procedure
> to make sure we never access the SPU any more during an
> ongoing save or even after that.
> 
> Thanks to Benjamin Herrenschmidt for pointing this out.
> 
Acked-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>

> Signed-off-by: Arnd Bergmann <arnd at arndb.de>
> 
> ---
> 
> Index: linux-2.6/arch/powerpc/platforms/cell/spufs/switch.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/switch.c
> +++ linux-2.6/arch/powerpc/platforms/cell/spufs/switch.c
> @@ -34,6 +34,7 @@
>  
>  #include <linux/module.h>
>  #include <linux/errno.h>
> +#include <linux/hardirq.h>
>  #include <linux/sched.h>
>  #include <linux/kernel.h>
>  #include <linux/mm.h>
> @@ -117,6 +118,8 @@ static inline void disable_interrupts(st
>  	 *     Write INT_MASK_class1 with value of 0.
>  	 *     Save INT_Mask_class2 in CSA.
>  	 *     Write INT_MASK_class2 with value of 0.
> +	 *     Synchronize all three interrupts to be sure
> +	 *     we no longer execute a handler on another CPU.
>  	 */
>  	spin_lock_irq(&spu->register_lock);
>  	if (csa) {
> @@ -129,6 +132,9 @@ static inline void disable_interrupts(st
>  	spu_int_mask_set(spu, 2, 0ul);
>  	eieio();
>  	spin_unlock_irq(&spu->register_lock);
> +	synchronize_irq(spu->irqs[0]);
> +	synchronize_irq(spu->irqs[1]);
> +	synchronize_irq(spu->irqs[2]);
>  }
>  
>  static inline void set_watchdog_timer(struct spu_state *csa, struct spu *spu)