On Wed, 4 May 2016, Lianwei Wang wrote:
> In this example, the unbalanced count is caused by the
> cpu_hotplug_pm_callback pm notifier callback function.
I doubt that.
> We can add a variable to avoid the unbalanced call of cpu_hotplug_enable
> ,e.g.
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 3e3f6e49eabb..aa6694f0e9d3 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -1140,16 +1140,21 @@ static int
> cpu_hotplug_pm_callback(struct notifier_block *nb,
> unsigned long action, void *ptr)
> {
> + static int disabled;
> +
> switch (action) {
>
> case PM_SUSPEND_PREPARE:
> case PM_HIBERNATION_PREPARE:
> cpu_hotplug_disable();
> + disabled = 1;
> break;
>
> case PM_POST_SUSPEND:
> case PM_POST_HIBERNATION:
> - cpu_hotplug_enable();
> + if (disabled)
> + cpu_hotplug_enable();
> + disabled = 0;
> break;
>
> default:
>
> Please let me know if you like to fix it in this way.
So you are moving the work around one step down w/o providing any reasonable
explanation how this asymetric call of that callback can happen.
Can you eventually come up with a coherent explanation of the problem down to
the root cause or are we going to play this "move the workaround one step
down" game for another 10 rounds?
> +static void _cpu_hotplug_enable(void)
> +{
> + if (WARN(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
> + return;
> +
> + cpu_hotplug_disabled--;
> +}
>
> I like to fix it in the cpu_hotplug_enable because it is a public
You CANNOT fix it there. The problem is the call site and NOT
cpu_hotplug_enable(). Can you finally accept this?
> kernel API and fix in it can prevent any other unbalanced calling. I
It cannot prevent any unbalanced calls. It mitigates the issue, but that's a
different problem.
We can discuss that seperately after fixing the offending call site.
Thanks,
tglx
