Re: [PATCH 3/3] relay: Add buffer-only channels; useful for early logging.

Re: [PATCH 3/3] relay: Add buffer-only channels; useful for early logging.

[Andrew Morton]

On Mon, 23 Jun 2008 15:31:04 +0300 Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro> wrote:

> Allows one to create and use a channel with no associated files. Files
> can be initialized later. This is useful in scenarios such as logging
> in early code, before VFS is up. Therefore, such channels can be
> created and used as soon as kmem_cache_init() completed.
> 
> This is needed by kmemtrace to do tracing in early kernel code.

This breaks on sparc64.

> +			err = smp_call_function_single(i,
> +						       __relay_set_buf_dentry,
> +						       &disp, 0, 1);

Because that ain't implemented.

There's a call in net/iucv/iucv.c, but that's s390-only.

There's a call in virt/kvm/kvm_main.c.

There's a call in kernel/time/tick-broadcast.c, so I assume that the
intersection between CONFIG_GENERIC_CLOCKEVENTS_BROADCAST and
non-smp_call_function_single() architectures is presently empty.


I guess all SMP-capable architectures should now implement this,
please.  It is presently defined on all architectures for CONFIG_SMP=n
and it is declared in include/linux/smp.h.

Re: [PATCH 3/3] relay: Add buffer-only channels; useful for early logging.

[Eduard - Gabriel Munteanu]

On Wed, 2 Jul 2008 23:06:36 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:
 
> This breaks on sparc64.
> 
> > +			err = smp_call_function_single(i,
> > +
> > __relay_set_buf_dentry,
> > +						       &disp, 0,
> > 1);
> 
> Because that ain't implemented.
> 
> There's a call in net/iucv/iucv.c, but that's s390-only.
> 
> There's a call in virt/kvm/kvm_main.c.
> 
> There's a call in kernel/time/tick-broadcast.c, so I assume that the
> intersection between CONFIG_GENERIC_CLOCKEVENTS_BROADCAST and
> non-smp_call_function_single() architectures is presently empty.

Hi,

I'm not sure what I should do. Maybe disable relay_late_setup_files()
on sparc64, with an empty inline?
 
> I guess all SMP-capable architectures should now implement this,
> please.  It is presently defined on all architectures for CONFIG_SMP=n
> and it is declared in include/linux/smp.h.

sparc64 seems to have smp_call_function_mask(). If we have the generic
kernel/smp.c in linux-next or -mmotm, then this will define
smp_call_function_single() to call smp_call_function_mask().

Is there anything I can do regarding this patch? Does it work since
kernel/smp.c reappeared?


	Eduard

Re: [PATCH 3/3] relay: Add buffer-only channels; useful for early logging.

[Andrew Morton]

On Sat, 5 Jul 2008 07:14:01 +0300 Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro> wrote:

> On Wed, 2 Jul 2008 23:06:36 -0700
> Andrew Morton <akpm@linux-foundation.org> wrote:
>  
> > This breaks on sparc64.
> > 
> > > +			err = smp_call_function_single(i,
> > > +
> > > __relay_set_buf_dentry,
> > > +						       &disp, 0,
> > > 1);
> > 
> > Because that ain't implemented.
> > 
> > There's a call in net/iucv/iucv.c, but that's s390-only.
> > 
> > There's a call in virt/kvm/kvm_main.c.
> > 
> > There's a call in kernel/time/tick-broadcast.c, so I assume that the
> > intersection between CONFIG_GENERIC_CLOCKEVENTS_BROADCAST and
> > non-smp_call_function_single() architectures is presently empty.
> 
> Hi,
> 
> I'm not sure what I should do.

Nothing, I'd suggest.  I think that all architectures should implement
smp_call_function_single().  You can have a shot at doing that if you
like, but the implementations will need to be reviewed and merged by
the relevant architectures maintainers.  (That's why I snuck linux-arch
into the cc list last time).

> Maybe disable relay_late_setup_files()
> on sparc64, with an empty inline?
>  
> > I guess all SMP-capable architectures should now implement this,
> > please.  It is presently defined on all architectures for CONFIG_SMP=n
> > and it is declared in include/linux/smp.h.
> 
> sparc64 seems to have smp_call_function_mask(). If we have the generic
> kernel/smp.c in linux-next or -mmotm, then this will define
> smp_call_function_single() to call smp_call_function_mask().
> 
> Is there anything I can do regarding this patch? Does it work since
> kernel/smp.c reappeared?

Nope:

y:/usr/src/25> grep USE_GENERIC_SMP_HELPERS arch/*/Kconfig
arch/alpha/Kconfig:     select USE_GENERIC_SMP_HELPERS
arch/arm/Kconfig:       select USE_GENERIC_SMP_HELPERS
arch/ia64/Kconfig:      select USE_GENERIC_SMP_HELPERS
arch/m32r/Kconfig:      select USE_GENERIC_SMP_HELPERS
arch/mips/Kconfig:      select USE_GENERIC_SMP_HELPERS
arch/parisc/Kconfig:    select USE_GENERIC_SMP_HELPERS
arch/powerpc/Kconfig:   select USE_GENERIC_SMP_HELPERS if SMP
arch/sh/Kconfig:        select USE_GENERIC_SMP_HELPERS
arch/x86/Kconfig:       select USE_GENERIC_SMP_HELPERS

It would help if you could check to see which architectures need work
and then perhaps propose patches.  If not, well, 2.6.27-rc1 will be
broken on some architectures on some configs and people will have a
couple of months to unbreak it.  Not a big problem, I expect.