netdev - Re: [PATCH] core: fix the use of this_cpu

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Date:	Thu, 28 Mar 2013 14:38:02 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
cc:	roy.qing.li@...il.com, Shan Wei <davidshan@...cent.com>,
	netdev@...r.kernel.org
Subject: Re: [PATCH] core: fix the use of this_cpu_ptr

On Thu, 28 Mar 2013, Eric Dumazet wrote:

> > flush_tasklet is not percpu var, and percpu is percpu var, and
> > 	this_cpu_ptr(&info->cache->percpu->flush_tasklet)
> > is not equal to
> > 	&this_cpu_ptr(info->cache->percpu)->flush_tasklet

&this_cpu_ptr is always an error since you are taking the addresss of an
address.

this_cpu_ptr(&structure) is the right way to get the address of the cpu
instance for this cpu for a per cpu structure.

> Christoph, could this kind of error be detected by the compiler or
> sparse ?

The per cpu variables are marked with __percpu. This should be detected by
sparse.

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