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

On 09/29/2012 03:45 AM, Nicolas Pitre wrote:

On Fri, 28 Sep 2012, Fan Wu wrote:

quoted

From: fwu <redacted>

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 <redacted>
Signed-off-by: YiLu Mao <redacted>
Signed-off-by: Ning Jiang <redacted>

This looks sensible to me.

Acked-by: Nicolas Pitre <redacted>

quoted

Change-Id: Iddacf45aec012bb663e130801727b4eb3d11436b

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

quoted

---
  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

Thanks a lot for reviewing the patch.
I'll remove that in the new patch version.
Thanks again.