Re: [PATCH] drivers/acpi/processor_driver.c: add missing kfree

[Julia Lawall]

On Wed, 14 Mar 2012, Srivatsa S. Bhat wrote:

> On 03/10/2012 10:35 PM, Julia Lawall wrote:
>
> > From: Julia Lawall <julia@xxxxxxx>
> >
> > 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@xxxxxxx>
> >
> > ---
> > 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.

Thanks for the feedback.  Just to be clear, I should keep

+err_clear_processors:
+       per_cpu(processors, pr->id) = NULL;

and just drop:

+       per_cpu(processor_device_array, pr->id) = NULL;

julia

> 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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