[PATCH] wireguard/queueing: simplify wg_cpumask_next_online()

[PATCH] wireguard/queueing: simplify wg_cpumask_next_online()

[Yury Norov]

wg_cpumask_choose_online() opencodes cpumask_nth(). Use it and make the
function significantly simpler. While there, fix opencoded cpu_online()
too. 

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 drivers/net/wireguard/queueing.h | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
index 7eb76724b3ed..3bfe16f71af0 100644
--- a/drivers/net/wireguard/queueing.h
+++ b/drivers/net/wireguard/queueing.h
@@ -104,17 +104,11 @@ static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating)
 
 static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
 {
-	unsigned int cpu = *stored_cpu, cpu_index, i;
+	if (likely(*stored_cpu < nr_cpu_ids && cpu_online(*stored_cpu)))
+		return cpu;
 
-	if (unlikely(cpu >= nr_cpu_ids ||
-		     !cpumask_test_cpu(cpu, cpu_online_mask))) {
-		cpu_index = id % cpumask_weight(cpu_online_mask);
-		cpu = cpumask_first(cpu_online_mask);
-		for (i = 0; i < cpu_index; ++i)
-			cpu = cpumask_next(cpu, cpu_online_mask);
-		*stored_cpu = cpu;
-	}
-	return cpu;
+	*stored_cpu = cpumask_nth(id % num_online_cpus(), cpu_online_mask);
+	return *stored_cpu;
 }
 
 /* This function is racy, in the sense that it's called while last_cpu is
-- 
2.43.0

Re: [PATCH] wireguard/queueing: simplify wg_cpumask_next_online()

[Yury Norov]

On Wed, Jun 04, 2025 at 07:36:55PM -0400, Yury Norov wrote:
> wg_cpumask_choose_online() opencodes cpumask_nth(). Use it and make the
> function significantly simpler. While there, fix opencoded cpu_online()
> too. 
> 
> Signed-off-by: Yury Norov <yury.norov@gmail.com>
> ---
>  drivers/net/wireguard/queueing.h | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
> index 7eb76724b3ed..3bfe16f71af0 100644
> --- a/drivers/net/wireguard/queueing.h
> +++ b/drivers/net/wireguard/queueing.h
> @@ -104,17 +104,11 @@ static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating)
>  
>  static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
>  {
> -	unsigned int cpu = *stored_cpu, cpu_index, i;
> +	if (likely(*stored_cpu < nr_cpu_ids && cpu_online(*stored_cpu)))
> +		return cpu;

Oops... This should be 
                return *stored_cpu;

I'll resend, sorry for noise.

>  
> -	if (unlikely(cpu >= nr_cpu_ids ||
> -		     !cpumask_test_cpu(cpu, cpu_online_mask))) {
> -		cpu_index = id % cpumask_weight(cpu_online_mask);
> -		cpu = cpumask_first(cpu_online_mask);
> -		for (i = 0; i < cpu_index; ++i)
> -			cpu = cpumask_next(cpu, cpu_online_mask);
> -		*stored_cpu = cpu;
> -	}
> -	return cpu;
> +	*stored_cpu = cpumask_nth(id % num_online_cpus(), cpu_online_mask);
> +	return *stored_cpu;
>  }
>  
>  /* This function is racy, in the sense that it's called while last_cpu is
> -- 
> 2.43.0

Re: [PATCH] wireguard/queueing: simplify wg_cpumask_next_online()

[Jason A. Donenfeld]

On Thu, Jun 05, 2025 at 12:23:29AM -0400, Yury Norov wrote:
> On Wed, Jun 04, 2025 at 07:36:55PM -0400, Yury Norov wrote:
> > wg_cpumask_choose_online() opencodes cpumask_nth(). Use it and make the
> > function significantly simpler. While there, fix opencoded cpu_online()
> > too. 
> > 
> > Signed-off-by: Yury Norov <yury.norov@gmail.com>
> > ---
> >  drivers/net/wireguard/queueing.h | 14 ++++----------
> >  1 file changed, 4 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
> > index 7eb76724b3ed..3bfe16f71af0 100644
> > --- a/drivers/net/wireguard/queueing.h
> > +++ b/drivers/net/wireguard/queueing.h
> > @@ -104,17 +104,11 @@ static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating)
> >  
> >  static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
> >  {
> > -	unsigned int cpu = *stored_cpu, cpu_index, i;
> > +	if (likely(*stored_cpu < nr_cpu_ids && cpu_online(*stored_cpu)))
> > +		return cpu;
> 
> Oops... This should be 
>                 return *stored_cpu;

Maybe it's best to structure the function something like:

unsigned int cpu = *stored_cpu;
if (unlikely(cpu >= nr_cpu_ids || !cpu_online(cpu))) {
	cpu = *stored_cpu = cpumask_nth(id % num_online_cpus(),	cpu_online_mask);
return cpu;

Re: [PATCH] wireguard/queueing: simplify wg_cpumask_next_online()

[Yury Norov]

On Thu, Jun 05, 2025 at 01:33:19PM +0200, Jason A. Donenfeld wrote:
> On Thu, Jun 05, 2025 at 12:23:29AM -0400, Yury Norov wrote:
> > On Wed, Jun 04, 2025 at 07:36:55PM -0400, Yury Norov wrote:
> > > wg_cpumask_choose_online() opencodes cpumask_nth(). Use it and make the
> > > function significantly simpler. While there, fix opencoded cpu_online()
> > > too. 
> > > 
> > > Signed-off-by: Yury Norov <yury.norov@gmail.com>
> > > ---
> > >  drivers/net/wireguard/queueing.h | 14 ++++----------
> > >  1 file changed, 4 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
> > > index 7eb76724b3ed..3bfe16f71af0 100644
> > > --- a/drivers/net/wireguard/queueing.h
> > > +++ b/drivers/net/wireguard/queueing.h
> > > @@ -104,17 +104,11 @@ static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating)
> > >  
> > >  static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
> > >  {
> > > -	unsigned int cpu = *stored_cpu, cpu_index, i;
> > > +	if (likely(*stored_cpu < nr_cpu_ids && cpu_online(*stored_cpu)))
> > > +		return cpu;
> > 
> > Oops... This should be 
> >                 return *stored_cpu;
> 
> Maybe it's best to structure the function something like:
> 
> unsigned int cpu = *stored_cpu;
> if (unlikely(cpu >= nr_cpu_ids || !cpu_online(cpu))) {
> 	cpu = *stored_cpu = cpumask_nth(id % num_online_cpus(),	cpu_online_mask);
> return cpu;

If you prefer. I'll send v2 shortly

Re: [PATCH] wireguard/queueing: simplify wg_cpumask_next_online()

[Jason A. Donenfeld]

On Thu, Jun 05, 2025 at 10:24:32AM -0400, Yury Norov wrote:
> On Thu, Jun 05, 2025 at 01:33:19PM +0200, Jason A. Donenfeld wrote:
> > On Thu, Jun 05, 2025 at 12:23:29AM -0400, Yury Norov wrote:
> > > On Wed, Jun 04, 2025 at 07:36:55PM -0400, Yury Norov wrote:
> > > > wg_cpumask_choose_online() opencodes cpumask_nth(). Use it and make the
> > > > function significantly simpler. While there, fix opencoded cpu_online()
> > > > too. 
> > > > 
> > > > Signed-off-by: Yury Norov <yury.norov@gmail.com>
> > > > ---
> > > >  drivers/net/wireguard/queueing.h | 14 ++++----------
> > > >  1 file changed, 4 insertions(+), 10 deletions(-)
> > > > 
> > > > diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h
> > > > index 7eb76724b3ed..3bfe16f71af0 100644
> > > > --- a/drivers/net/wireguard/queueing.h
> > > > +++ b/drivers/net/wireguard/queueing.h
> > > > @@ -104,17 +104,11 @@ static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating)
> > > >  
> > > >  static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
> > > >  {
> > > > -	unsigned int cpu = *stored_cpu, cpu_index, i;
> > > > +	if (likely(*stored_cpu < nr_cpu_ids && cpu_online(*stored_cpu)))
> > > > +		return cpu;
> > > 
> > > Oops... This should be 
> > >                 return *stored_cpu;
> > 
> > Maybe it's best to structure the function something like:
> > 
> > unsigned int cpu = *stored_cpu;
> > if (unlikely(cpu >= nr_cpu_ids || !cpu_online(cpu))) {
> > 	cpu = *stored_cpu = cpumask_nth(id % num_online_cpus(),	cpu_online_mask);
> > return cpu;
> 
> If you prefer. I'll send v2 shortly

While you're at it, fix the commit subject to match the format used by
every single other wireguard commit. `$ git log --oneline drivers/net/wireguard`
to see what I mean.

Re: [PATCH] wireguard/queueing: simplify wg_cpumask_next_online()

[kernel test robot]

Hi Yury,

kernel test robot noticed the following build errors:

[auto build test ERROR on linus/master]
[also build test ERROR on crng-random/master v6.16-rc2 next-20250618]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Yury-Norov/wireguard-queueing-simplify-wg_cpumask_next_online/20250605-073832
base:   linus/master
patch link:    https://lore.kernel.org/r/20250604233656.41896-1-yury.norov%40gmail.com
patch subject: [PATCH] wireguard/queueing: simplify wg_cpumask_next_online()
config: nios2-allyesconfig (https://download.01.org/0day-ci/archive/20250618/202506181915.j2LnH7Ai-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250618/202506181915.j2LnH7Ai-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202506181915.j2LnH7Ai-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from drivers/net/wireguard/main.c:9:
   drivers/net/wireguard/queueing.h: In function 'wg_cpumask_choose_online':
>> drivers/net/wireguard/queueing.h:108:24: error: 'cpu' undeclared (first use in this function)
     108 |                 return cpu;
         |                        ^~~
   drivers/net/wireguard/queueing.h:108:24: note: each undeclared identifier is reported only once for each function it appears in


vim +/cpu +108 drivers/net/wireguard/queueing.h

e7096c131e5161f Jason A. Donenfeld 2019-12-09  104  
e7096c131e5161f Jason A. Donenfeld 2019-12-09  105  static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id)
e7096c131e5161f Jason A. Donenfeld 2019-12-09  106  {
b74b49327e49f39 Yury Norov         2025-06-04  107  	if (likely(*stored_cpu < nr_cpu_ids && cpu_online(*stored_cpu)))
e7096c131e5161f Jason A. Donenfeld 2019-12-09 @108  		return cpu;
b74b49327e49f39 Yury Norov         2025-06-04  109  
b74b49327e49f39 Yury Norov         2025-06-04  110  	*stored_cpu = cpumask_nth(id % num_online_cpus(), cpu_online_mask);
b74b49327e49f39 Yury Norov         2025-06-04  111  	return *stored_cpu;
e7096c131e5161f Jason A. Donenfeld 2019-12-09  112  }
e7096c131e5161f Jason A. Donenfeld 2019-12-09  113  

-- 
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https://github.com/intel/lkp-tests/wiki