Messages in this thread | | | Date | Thu, 5 May 2016 14:13:06 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH] cpu/hotplug: handle unbalanced hotplug enable/disable |
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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
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