Re: [next:akpm 129/309] net/core/sock.c:274:36: error: initializer element is not constant

[Mel Gorman <mgorman@suse.de>]

On Mon, Jul 23, 2012 at 12:20:20PM +0100, James Bottomley wrote:
> [Parisc list cc added]
> On Mon, 2012-07-23 at 12:16 +0100, Mel Gorman wrote:
> > On Mon, Jul 23, 2012 at 12:30:58AM +0800, Fengguang Wu wrote:
> > > Hi Mel,
> > > 
> > > To be frank, I don't quite understand this build failure..
> > > 
> > > tree:   next/akpm akpm
> > > head:   37e2ad4953983527f7bdb6831bf478eedcc84082
> > > commit: 799dc3a908b1df8b766c35aefc24c1b5356aa051 [129/309] netvm: allow skb allocation to use PFMEMALLOC reserves
> > > config: parisc-defconfig (attached as .config)
> > > 
> > > All related error/warning messages:
> > > 
> > > net/core/sock.c:274:36: error: initializer element is not constant
> > > net/core/sock.c:274:36: error: (near initialization for 'memalloc_socks')
> > > net/core/sock.c:274:36: error: initializer element is not constant
> > > 
> > 
> > It looks parisc specific so am adding some parisc because this builds but
> > I am less sure if it is actually correct. If it's correct, it should be
> > appear before the swap-over-nfs patches to avoid bisection problems.
> > I've added some parisc folk for review.
> > 
> > ---8<---
> > parisc: Redefine ATOMIC_INIT and ATOMIC64_INIT like other architectures
> > 
> > The following build error occured during a parisc build with
> > swap-over-NFS patches applied.
> > 
> > net/core/sock.c:274:36: error: initializer element is not constant
> > net/core/sock.c:274:36: error: (near initialization for 'memalloc_socks')
> > net/core/sock.c:274:36: error: initializer element is not constant
> > 
> > It's not obvious but this is due to how ATOMIC_INIT is defined on
> > parisc. It should affect any user of STATIC_KEY_INIT_FALSE on that
> > platform.
> > 
> > This patch makes the definition of ATOMIC_INIT on parisc to look like
> > other arches definition.
> > 
> > Reported-by: Fengguang Wu <fengguang.wu@intel.com>
> > Signed-off-by: Mel Gorman <mgorman@suse.de>
> > ---
> >  arch/parisc/include/asm/atomic.h |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/parisc/include/asm/atomic.h b/arch/parisc/include/asm/atomic.h
> > index 6c6defc..af9cf30 100644
> > --- a/arch/parisc/include/asm/atomic.h
> > +++ b/arch/parisc/include/asm/atomic.h
> > @@ -141,7 +141,7 @@ static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u)
> >  
> >  #define atomic_sub_and_test(i,v)	(atomic_sub_return((i),(v)) == 0)
> >  
> > -#define ATOMIC_INIT(i)	((atomic_t) { (i) })
> > +#define ATOMIC_INIT(i)	{ (i) }
> >  
> >  #define smp_mb__before_atomic_dec()	smp_mb()
> >  #define smp_mb__after_atomic_dec()	smp_mb()
> > @@ -150,7 +150,7 @@ static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u)
> >  
> >  #ifdef CONFIG_64BIT
> >  
> > -#define ATOMIC64_INIT(i) ((atomic64_t) { (i) })
> > +#define ATOMIC64_INIT(i) { (i) }
> >  
> >  static __inline__ s64
> >  __atomic64_add_return(s64 i, atomic64_t *v)
> 
> OK, I don't understand this either ... why would not casting to the
> appropriate type suddenly stop warning about the initialiser being non
> constant.  It looks like some type of gcc bug to me. 

I agree. I could not see any functional difference as such either but also
could not figure out why gcc would get it right for some arches and not
for others.

> Our toolchain
> expert (Dave) hangs out on the parisc list ... he'll want to know your
> gcc -v.
> 

I'm using the cross-compiler from
ftp://ftp.kernel.org/pub/tools/crosstool/files/bin/x86_64/4.6.3/. I do
not know what compiler Fengguang Wu was using. 

Using built-in specs.
COLLECT_GCC=/home/mel/git-public/cross-compilers/gcc-4.6.3-nolibc/hppa-linux/bin/hppa-linux-gcc
COLLECT_LTO_WRAPPER=/home/mel/git-public/cross-compilers/gcc-4.6.3-nolibc/hppa-linux/bin/../libexec/gcc/hppa-linux/4.6.3/lto-wrapper
Target: hppa-linux
Configured with: /home/tony/buildall/src/gcc/configure
--target=hppa-linux --host=x86_64-linux-gnu --build=x86_64-linux-gnu
--enable-targets=all --prefix=/opt/cross/gcc-4.6.3-nolibc/hppa-linux/
--enable-languages=c --with-newlib --without-headers
--enable-sjlj-exceptions --with-system-libunwind --disable-nls
--disable-threads --disable-shared --disable-libmudflap --disable-libssp
--disable-libgomp --disable-decimal-float --enable-checking=release
--with-mpfr=/home/tony/buildall/src/sys-x86_64
--with-gmp=/home/tony/buildall/src/sys-x86_64 --disable-bootstrap
--disable-libquadmath
Thread model: single
gcc version 4.6.3 (GCC) 

-- 
Mel Gorman
SUSE Labs