From: Josh Triplett <josh@kernel.org>
To: Tejun Heo <tj@kernel.org>
Cc: Wanlong Gao <gaowanlong@cn.fujitsu.com>,
linux-sparse@vger.kernel.org,
Wu Fengguang <fengguang.wu@intel.com>,
kbuild-all@01.org, Rusty Russell <rusty@rustcorp.com.au>,
Christoph Lameter <cl@linux-foundation.org>
Subject: Re: [BUG report]sparse warnings on DEFINE_PER_CPU() symbols non-static
Date: Tue, 3 Dec 2013 15:43:20 -0800 [thread overview]
Message-ID: <20131203234320.GA15141@jtriplet-mobl1> (raw)
In-Reply-To: <20131203222543.GQ8277@htj.dyndns.org>
On Tue, Dec 03, 2013 at 05:25:43PM -0500, Tejun Heo wrote:
> Hello,
>
> On Tue, Nov 26, 2013 at 11:37:03AM +0800, Wanlong Gao wrote:
> > If kernel config CONFIG_DEBUG_FORCE_WEAK_PER_CPU=y, then the sparse will report non-static
> > warnings like following:
> >
> > > /git/linux/fs/inode.c:74:8: warning: symbol 'nr_inodes' was not declared. Should it be static?
> > > /git/linux/fs/inode.c:75:8: warning: symbol 'nr_unused' was not declared. Should it be static?
> > >
> > > $ vi +74 fs/inode.c
> > > 73
> > > 74 static DEFINE_PER_CPU(unsigned long, nr_inodes);
> > > 75 static DEFINE_PER_CPU(unsigned long, nr_unused);
> > > 76
>
> Hmmm, so, if FORCE_WEAK_PER_CPU is set or the arch needs WEAK_PER_CPU,
> DEFINE_PER_CPU() explodes into mind-bending series of definitions to
> ensure that the symbol is globally unique to avoid breaking weak decl
> requirements on a few archs. In the process static is dropped from
> the actual declaration and it's apparently missing extern decl in
> front of it.
>
> Does the following patch make it go away?
It should, but is there some reason why you couldn't make the definition
on the line immediately below that static?
> Thanks.
>
> diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
> index 57e890a..8c490cc 100644
> --- a/include/linux/percpu-defs.h
> +++ b/include/linux/percpu-defs.h
> @@ -69,6 +69,7 @@
> __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
> extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
> __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
> + extern __typeof__(type) name; \
> __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \
> __typeof__(type) name
> #else
> --
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next prev parent reply other threads:[~2013-12-03 23:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-26 3:37 [BUG report]sparse warnings on DEFINE_PER_CPU() symbols non-static Wanlong Gao
2013-12-03 22:25 ` Tejun Heo
2013-12-03 23:43 ` Josh Triplett [this message]
2013-12-04 15:10 ` Tejun Heo
2013-12-04 3:26 ` Wanlong Gao
2013-12-04 15:12 ` Tejun Heo
2013-12-05 0:18 ` Wanlong Gao
2013-12-05 18:01 ` [PATCH] percpu: fix spurious sparse warnings from DEFINE_PER_CPU() Tejun Heo
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