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SubjectRe: [PATCH] drivers/acpi/processor_driver.c: add missing kfree
On 03/10/2012 10:35 PM, Julia Lawall wrote:

> From: Julia Lawall <julia@diku.dk>
>
> The function acpi_processor_add is stored in the ops.add field of a
> acpi_driver structure. This function is then called in
> acpi_bus_driver_init. On failure, this function clears the field
> device->driver_data, but does not free its contents. Thus the free has to
> be done by the add function. In acpi_processor_add, the corresponding
> value is pr. This value is currently freed on failure before storing it in
> device->driver_data, but not after. This free is added in the error
> handling code at the end of the function. The static global variable


"static global variable"?? never heard that one before ;-)
Maybe you meant "per_cpu variable processors"..

> processors is also cleared so that it does not refer to a dangling pointer.
> processor_device_array is cleared as well.
>
> Signed-off-by: Julia Lawall <julia@diku.dk>
>
> ---
> This is only compile tested. In particular, I don't know if it is correct
> to add per_cpu(processor_device_array, pr->id) = NULL;.


No, you shouldn't set it to NULL. processor_device_array was added to check
for buggy BIOSes and return gracefully. Check commit cd8e2b48d (and also the
bugzilla link in that commit).

To have a robust check for buggy BIOSes, we must let it be as it is, even if
it is a stale pointer. That way we can still catch subsequent calls to this
function with the same acpi id (because of a buggy BIOS) and take appropriate
actions.

Other than that, the patch looks good to me.

Regards,
Srivatsa S. Bhat
IBM Linux Technology Center

> It has nothing to
> do with pr, but it looks like stale information in the case of a failure.
>
> drivers/acpi/processor_driver.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> index 2801b41..9bb0017 100644
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -536,8 +536,8 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
> return -ENOMEM;
>
> if (!zalloc_cpumask_var(&pr->throttling.shared_cpu_map, GFP_KERNEL)) {
> - kfree(pr);
> - return -ENOMEM;
> + result = -ENOMEM;
> + goto err_free_pr;
> }
>
> pr->handle = device->handle;
> @@ -577,7 +577,7 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
> dev = get_cpu_device(pr->id);
> if (sysfs_create_link(&device->dev.kobj, &dev->kobj, "sysdev")) {
> result = -EFAULT;
> - goto err_free_cpumask;
> + goto err_clear_processors;
> }
>
> /*
> @@ -595,9 +595,13 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
>
> err_remove_sysfs:
> sysfs_remove_link(&device->dev.kobj, "sysdev");
> +err_clear_processors:
> + per_cpu(processors, pr->id) = NULL;
> + per_cpu(processor_device_array, pr->id) = NULL;
> err_free_cpumask:
> free_cpumask_var(pr->throttling.shared_cpu_map);
> -
> +err_free_pr:
> + kfree(pr);
> return result;
> }
>
>



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