Hi Paul,
On Thu, 7 Jan 2016 10:02:44 -0800 "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Jan 07, 2016 at 07:57:25PM +1100, Stephen Rothwell wrote:
> > Hi Paul,
> >
> > [I found this a few days ago, but I think I forgot to send the email,
> > sorry.]
> >
> > After merging the rcu tree, today's linux-next build (powerpc
> > allyesconfig) failed like this:
> >
> > kernel/rcu/rcuperf.o:(.discard+0x0): multiple definition of `__pcpu_unique_srcu_ctl_srcu_array'
> > kernel/rcu/rcutorture.o:(.discard+0x0): first defined here
> >
> > Caused by commit
> >
> > abcd7ec0808e ("rcutorture: Add RCU grace-period performance tests")
> >
> > I have reverted that commit for today.
>
> Hello, Stephen,
>
> Very strange. The "static" keyword does not mean anything here?
> Easy enough to use different symbols in the two different files,
> but this situation is not so good for information hiding.
>
> Happy to update rcuperf.c to use a different name, but in the
> immortal words of MSDOS, "Are you sure?" :-)
I have no idea why it happens, but I do get the error above unless I
revert that commit. So, yes, I am sure :-)
OK, I looked further and
DEFINE_STATIC_SRCU(srcu_ctl);
becomes this (NLs added for clarity):
static __attribute__((section(".discard"), unused)) char __pcpu_scope_srcu_ctl_srcu_array;
extern __attribute__((section(".discard"), unused)) char __pcpu_unique_srcu_ctl_srcu_array;
__attribute__((section(".discard"), unused)) char __pcpu_unique_srcu_ctl_srcu_array;
extern __attribute__((section(".data..percpu" ""))) __typeof__(struct srcu_struct_array) srcu_ctl_srcu_array;
__attribute__((section(".data..percpu" ""))) __attribute__((weak)) __typeof__(struct srcu_struct_array) srcu_ctl_srcu_array;
static struct srcu_struct srcu_ctl = {
.
.
};
So, the "static" is not very effective :-(
--
Cheers,
Stephen Rothwell sfr@xxxxxxxxxxxxxxxx
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