nohz: replace dead select with choice default

[PATCH] nohz: replace dead select with choice default

Posted by Julian Braha 2 months ago

'select' does not work on config options in a 'choice', so currently the
'select VIRT_CPU_ACCOUNTING_GEN' for NO_HZ_FULL is dead, with the choice
option VIRT_CPU_ACCOUNTING_GEN only being enabled when NO_HZ_FULL=y because
the other choice members depend on NO_HZ_FULL=n.

Let's remove the dead select, and encode this relationship as a default of
the choice, instead.

This dead select was found by kconfirm, a static analysis tool for Kconfig.

Signed-off-by: Julian Braha <julianbraha@gmail.com>
---
 init/Kconfig        | 1 +
 kernel/time/Kconfig | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index 544167a7045d..8583d9f06c52 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -565,6 +565,7 @@ config VIRT_CPU_ACCOUNTING
 
 choice
 	prompt "Cputime accounting"
+	default VIRT_CPU_ACCOUNTING_GEN if NO_HZ_FULL
 	default TICK_CPU_ACCOUNTING
 
 # Kind of a stub config for the pure tick based cputime accounting
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index d098ac39bde4..ddfb6bee0745 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -133,7 +133,6 @@ config NO_HZ_FULL
 	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
 	select NO_HZ_COMMON
 	select RCU_NOCB_CPU
-	select VIRT_CPU_ACCOUNTING_GEN
 	select IRQ_WORK
 	select CPU_ISOLATION
 	help
-- 
2.55.0

Re: [PATCH] nohz: replace dead select with choice default

Posted by Nicolas Schier 2 months ago

On Sat, Aug 01, 2026 at 05:01:40PM +0100, Julian Braha wrote:
> 'select' does not work on config options in a 'choice', so currently the
> 'select VIRT_CPU_ACCOUNTING_GEN' for NO_HZ_FULL is dead, with the choice
> option VIRT_CPU_ACCOUNTING_GEN only being enabled when NO_HZ_FULL=y because
> the other choice members depend on NO_HZ_FULL=n.
> 
> Let's remove the dead select, and encode this relationship as a default of
> the choice, instead.
> 
> This dead select was found by kconfirm, a static analysis tool for Kconfig.
> 
> Signed-off-by: Julian Braha <julianbraha@gmail.com>
> ---
>  init/Kconfig        | 1 +
>  kernel/time/Kconfig | 1 -
>  2 files changed, 1 insertion(+), 1 deletion(-)
> 

Thanks!

Reviewed-by: Nicolas Schier <nsc@kernel.org>

Re: [PATCH] nohz: replace dead select with choice default

Posted by Bradley Morgan 2 months ago

Thanks for the patch Julian.

Please add:

Reviewed-by: Bradley Morgan <include@grrlz.net>

Thanks!

[tip: timers/core] nohz: Replace dead select with choice default

Posted by tip-bot2 for Julian Braha 1 month, 3 weeks ago

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     b17006b45283f012a6e166517f5ca3e1af2f806a
Gitweb:        https://git.kernel.org/tip/b17006b45283f012a6e166517f5ca3e1af2f806a
Author:        Julian Braha <julianbraha@gmail.com>
AuthorDate:    Sat, 01 Aug 2026 17:01:40 +01:00
Committer:     Thomas Gleixner <tglx@kernel.org>
CommitterDate: Tue, 11 Aug 2026 15:37:23 +02:00

nohz: Replace dead select with choice default

'select' does not work on config options in a 'choice', so currently the
'select VIRT_CPU_ACCOUNTING_GEN' for NO_HZ_FULL is dead, with the choice
option VIRT_CPU_ACCOUNTING_GEN only being enabled when NO_HZ_FULL=y because
the other choice members depend on NO_HZ_FULL=n.

Remove the dead select, and encode this relationship as a default of the
choice, instead.

This dead select was found by kconfirm, a static analysis tool for Kconfig.

Signed-off-by: Julian Braha <julianbraha@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Bradley Morgan <include@grrlz.net>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20260801160140.2391000-1-julianbraha@gmail.com
---
 init/Kconfig        | 1 +
 kernel/time/Kconfig | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index 5230d48..523e41d 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -562,6 +562,7 @@ config VIRT_CPU_ACCOUNTING
 
 choice
 	prompt "Cputime accounting"
+	default VIRT_CPU_ACCOUNTING_GEN if NO_HZ_FULL
 	default TICK_CPU_ACCOUNTING
 
 # Kind of a stub config for the pure tick based cputime accounting
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index d098ac3..ddfb6be 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -133,7 +133,6 @@ config NO_HZ_FULL
 	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
 	select NO_HZ_COMMON
 	select RCU_NOCB_CPU
-	select VIRT_CPU_ACCOUNTING_GEN
 	select IRQ_WORK
 	select CPU_ISOLATION
 	help