Re: [linux-pm] [PATCH 2.6.25-rc1] cpufreq: fix cpufreq policy refcount imbalance

Alan Stern
2008-02-15T15:52:52Z

On Fri, 15 Feb 2008, Yi Yang wrote:

> This patch adds kobject_put to balance refcount. I noticed Greg suggests
> it will fix a power-off issue to remove kobject_get statement block, but i
> think that isn't the best way because those code block has existed very long
> and it is helpful because the successive statements are invoking relevant
> data.

Are you referring to this section of code (before the region affected
by your patch)?

if (!kobject_get(&data->kobj)) {
spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
cpufreq_debug_enable_ratelimit();
unlock_policy_rwsem_write(cpu);
return -EFAULT;
}

Greg is correct that the kobject_get() here is useless and should be
removed. kobject_get() never returns NULL unless its argument is NULL.
Since &data->kobj can never be NULL, the "if" test will never fail.
Hence there's no point in making the test at all.

The fact that a section of code has existed for a long time doesn't
mean that it is right. :-)

Furthermore, there's no reason to do the kobject_get(). Holding 2
references to a kobject is no better than holding just 1 reference.
Assuming you know that the kobject is still registered, then you also
know that there is already a reference to it. So you have no reason to
take an additional reference.

Alan Stern