[PATCH] ARM: Add BUG_ON when hlt counter is wrongly used

[Nicolas Pitre]

On Fri, 28 Sep 2012, Fan Wu wrote:

> From: fwu <fwu at marvell.com>
> 
> 1. On ARM platform, "nohlt" can be used to prevent core from idle
>    process, returning immediately.
> 2. There are two interfaces, exported for other modules, named
>    "disable_hlt" and "enable_hlt" are used to enable/disable the
>    cpuidle mechanism by increasing/decreasing "hlt_counter".
>    Disable_hlt and enable_hlt are paired operation,
>    when you first call disable_hlt and then enable_hlt, the
>    semantics are right.
> 3. There is no obvious constraint to prevent user(driver/module)
>    code to prevent the case that enable_hlt is ahead of disable_hlt,
>    which is a fatal operation on kernel state change from user,
>    and there is no any WARNING or notification if the case happens
>    in current kernel code.
>    This patch aims to report BUG when the case happens, just like
>    what the kernel do when enable_irq is ahead of disable_irq.
> 
> Signed-off-by: fwu <fwu at marvell.com>
> Signed-off-by: YiLu Mao <ylmao at marvell.com>
> Signed-off-by: Ning Jiang <ning.jiang at marvell.com>

This looks sensible to me.

Acked-by: Nicolas Pitre <nico at linaro.org>

> Change-Id: Iddacf45aec012bb663e130801727b4eb3d11436b

Please don't forget to strip that when submitting your patch to 
Russell's patch system.

> ---
>  arch/arm/kernel/process.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> index 693b744..5bbd3be 100644
> --- a/arch/arm/kernel/process.c
> +++ b/arch/arm/kernel/process.c
> @@ -70,6 +70,7 @@ EXPORT_SYMBOL(disable_hlt);
>  void enable_hlt(void)
>  {
>  	hlt_counter--;
> +	BUG_ON(hlt_counter < 0)
>  }
>  
>  EXPORT_SYMBOL(enable_hlt);
> -- 
> 1.7.0.4
>