[PATCH] cpumask: provide a dummy cpumask_next_wrap

[PATCH] cpumask: provide a dummy cpumask_next_wrap

[Arnd Bergmann]

The virtio_net driver has become the first one to call cpumask_next_wrap()
even if CONFIG_SMP is disabled, leading to a build error:

drivers/net/virtio_net.c: In function 'virtnet_set_affinity':
drivers/net/virtio_net.c:1916:10: error: implicit declaration of function 'cpumask_next_wrap'; did you mean 'cpumask_next_and'? [-Werror=implicit-function-declaration]
    cpu = cpumask_next_wrap(cpu, cpu_online_mask,

Add a stub function along the lines of cpumask_first(), cpumask_next() etc.
I'm not entirely sure what should be returned in this case, but at
least for virtio_net, anything should work.

Fixes: 2ca653d607ce ("virtio_net: Stripe queue affinities across cores.")
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Caleb Raitto <caraitto@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 include/linux/cpumask.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 57f20a0a7794..079ba06309bd 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -159,6 +159,11 @@ static inline unsigned int cpumask_next_and(int n,
 	return n+1;
 }
 
+static inline int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
+{
+	return n;
+}
+
 /* cpu must be a valid cpu, ie 0, so there's no other choice. */
 static inline unsigned int cpumask_any_but(const struct cpumask *mask,
 					   unsigned int cpu)
-- 
2.18.0

Re: [PATCH] cpumask: provide a dummy cpumask_next_wrap

[Caleb Raitto]

On Mon, Aug 13, 2018 at 2:55 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> The virtio_net driver has become the first one to call cpumask_next_wrap()
> even if CONFIG_SMP is disabled, leading to a build error:
>
> drivers/net/virtio_net.c: In function 'virtnet_set_affinity':
> drivers/net/virtio_net.c:1916:10: error: implicit declaration of function 'cpumask_next_wrap'; did you mean 'cpumask_next_and'? [-Werror=implicit-function-declaration]
>     cpu = cpumask_next_wrap(cpu, cpu_online_mask,
>
> Add a stub function along the lines of cpumask_first(), cpumask_next() etc.
> I'm not entirely sure what should be returned in this case, but at
> least for virtio_net, anything should work.

Sorry about the build break, I think this patch with a fix was already merged:

cpumask: make cpumask_next_wrap available without smp
https://patchwork.ozlabs.org/patch/956670/

Thanks,
-Caleb

Re: [PATCH] cpumask: provide a dummy cpumask_next_wrap

[Arnd Bergmann]

On Tue, Aug 14, 2018 at 12:02 AM Caleb Raitto <caraitto@google.com> wrote:
>
> On Mon, Aug 13, 2018 at 2:55 PM Arnd Bergmann <arnd@arndb.de> wrote:
> >
> > The virtio_net driver has become the first one to call cpumask_next_wrap()
> > even if CONFIG_SMP is disabled, leading to a build error:
> >
> > drivers/net/virtio_net.c: In function 'virtnet_set_affinity':
> > drivers/net/virtio_net.c:1916:10: error: implicit declaration of function 'cpumask_next_wrap'; did you mean 'cpumask_next_and'? [-Werror=implicit-function-declaration]
> >     cpu = cpumask_next_wrap(cpu, cpu_online_mask,
> >
> > Add a stub function along the lines of cpumask_first(), cpumask_next() etc.
> > I'm not entirely sure what should be returned in this case, but at
> > least for virtio_net, anything should work.
>
> Sorry about the build break, I think this patch with a fix was already merged:
>
> cpumask: make cpumask_next_wrap available without smp
> https://patchwork.ozlabs.org/patch/956670/

Ok, that's also a better fix than mine I think.

Thanks,

        Arnd

Re: [PATCH] cpumask: provide a dummy cpumask_next_wrap

[David Miller]

From: Arnd Bergmann <arnd@arndb.de>
Date: Mon, 13 Aug 2018 23:55:16 +0200

> The virtio_net driver has become the first one to call cpumask_next_wrap()
> even if CONFIG_SMP is disabled, leading to a build error:
> 
> drivers/net/virtio_net.c: In function 'virtnet_set_affinity':
> drivers/net/virtio_net.c:1916:10: error: implicit declaration of function 'cpumask_next_wrap'; did you mean 'cpumask_next_and'? [-Werror=implicit-function-declaration]
>     cpu = cpumask_next_wrap(cpu, cpu_online_mask,
> 
> Add a stub function along the lines of cpumask_first(), cpumask_next() etc.
> I'm not entirely sure what should be returned in this case, but at
> least for virtio_net, anything should work.
> 
> Fixes: 2ca653d607ce ("virtio_net: Stripe queue affinities across cores.")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

This should already be fixed in my tree, and:

> +static inline int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
> +{
> +	return n;
> +}

this doesn't handle the "n==0 && wrap" case properly, in that situation you should
return '1'.