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SubjectRe: [PATCH hw_breakpoint] percpu: add __percpu sparse annotations to hw_breakpoint
Hello,

On 02/18/2010 01:39 AM, Frederic Weisbecker wrote:
> On Wed, Feb 17, 2010 at 10:50:50AM +0900, Tejun Heo wrote:
> Yeah, looks good, I'm queuing it.
> Just few comments below, for nano-considerations.
>> cpu_events = alloc_percpu(typeof(*cpu_events));
>> if (!cpu_events)
>> - return ERR_PTR(-ENOMEM);
>> + return (void __percpu __force *)ERR_PTR(-ENOMEM);
>
> Is this pattern common enough that we can think about a ERR_CPU_PTR ?

I thought about that but there aren't too many yet, so I just added
the ugly castings. It would be cool if sparse can be taught that
ERR_PTR() returns universal pseudo pointer.

>> sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler);
>> - if (IS_ERR(sample_hbp)) {
>> - ret = PTR_ERR(sample_hbp);
>> + if (IS_ERR((void __force *)sample_hbp)) {
>> + ret = PTR_ERR((void __force *)sample_hbp);
>
> Same comments here, although I wouldn't like much a CPU_PTR_ERR or
> IS_ERR_CPU.... CPP is just so poor in magic for that.
>
> I must confess I miss a bit the old per_cpu prefix that guarded the implicit
> separate namespace.

Yeap, I agree that the prefix had its advantages. It's just that it
can't scale to the new situation where static and dynamic percpu
variables behave uniformly.

Thank you.

--
tejun


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