linux-kernel - Re: [PATCH hw_breakpoint] percpu: add __percpu sparse annotations to hw

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Message-ID: <4B7C8E84.2030701@kernel.org>
Date:	Thu, 18 Feb 2010 09:49:08 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	lkml <linux-kernel@...r.kernel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [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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