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

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Date:	Thu, 28 Mar 2013 16:44:37 +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:

> On Thu, 2013-03-28 at 14:38 +0000, Christoph Lameter wrote:
> > On Thu, 28 Mar 2013, Eric Dumazet wrote:
>
> >
> > > 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.
>
> make C=2 net/core/flow.o
>
>   CHECK   net/core/flow.c
>
> No warning.

huh?

this_cpu_ptr uses SHIFT_PERCPU_PTR


#ifndef SHIFT_PERCPU_PTR
/* Weird cast keeps both GCC and sparse happy. */
#define SHIFT_PERCPU_PTR(__p, __offset) ({                              \
        __verify_pcpu_ptr((__p));                                       \
        RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset));
\
})
#endif

This would mean that __verify_pcpu_ptr is broken.


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