On Wed, 21 Dec 2016, Thomas Gleixner wrote:
> The cpu hotplug support of this perf driver is broken in several ways:
>
> 1) It adds a instance before setting up the state.
>
> 2) The state for the instance is different from the state of the
> callback. It's just a randomly chosen state.
>
> 3) The instance registration is not error checked so nobody noticed that
> the call can never succeed.
>
> 4) The state for the multi install callbacks is chosen randomly and
> overwrites existing state. This is now prevented by the core code so the
> call is guaranteed to fail.
>
> 5) The error exit path in the init function leaves the instance registered
> and then frees the memory which contains the enqueued hlist node.
>
> 6) The remove function is removing the state and not the instance.
>
> Fix it by:
>
> - Setting up the state before adding instances. Use a dynamically allocated
> state for it.
>
> - Install instances after the state has been set up
>
> - Remove the instance in the error path before freeing memory
>
> - Remove instance not the state in the driver remove callback
>
> While at is use raw_cpu_processor_id(), because cpu_processor_id() cannot
> be used in preemptible context, and set the driver data after successful
> registration of the pmu.
>
> Fixes: e76bdfd7403a ("ARM: imx: Added perf functionality to mmdc driver")
> Signed-off-by: Thomas Gleixner <[email protected]>
> Cc: Zhengyu Shen <[email protected]>
> Cc: Frank Li <[email protected]>
> Cc: Shawn Guo <[email protected]>
Shawn,
as I have the final hotplug notifier removal pending here, which will break
also the compilation of this driver, I would prefer to merge that through
my tree before the removal patches to avoid build breakage.
Thanks,
tglx
