[PATCH] powerpc: Remove dead non-preemption code

[PATCH] powerpc: Remove dead non-preemption code

[Christophe Leroy (CS GROUP)]

Since commit 7dadeaa6e851 ("sched: Further restrict the preemption
modes"), powerpc always has CONFIG_PREEMPTION because only
CONFIG_PREEMPT and CONFIG_PREEMPT_LAZY are possible, even in
dynamic preemption mode (see sched_dynamic_mode).

As a consequence, need_irq_preemption() is always true and can be
removed.

And because commit bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY
feature") includes linux/irq-entry-common.h which already declares
sk_dynamic_irqentry_exit_cond_resched static key, asm/preempt.h
becauses useless and can be removed.

Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
---
 arch/powerpc/include/asm/preempt.h | 16 ----------------
 arch/powerpc/lib/vmx-helper.c      |  2 +-
 2 files changed, 1 insertion(+), 17 deletions(-)
 delete mode 100644 arch/powerpc/include/asm/preempt.h

diff --git a/arch/powerpc/include/asm/preempt.h b/arch/powerpc/include/asm/preempt.h
deleted file mode 100644
index 000e2b9681f3..000000000000
--- a/arch/powerpc/include/asm/preempt.h
+++ /dev/null
@@ -1,16 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef __ASM_POWERPC_PREEMPT_H
-#define __ASM_POWERPC_PREEMPT_H
-
-#include <asm-generic/preempt.h>
-
-#if defined(CONFIG_PREEMPT_DYNAMIC)
-#include <linux/jump_label.h>
-DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
-#define need_irq_preemption() \
-	(static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
-#else
-#define need_irq_preemption()   (IS_ENABLED(CONFIG_PREEMPTION))
-#endif
-
-#endif /* __ASM_POWERPC_PREEMPT_H */
diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c
index 57e897b60db8..cc9fb72cb4eb 100644
--- a/arch/powerpc/lib/vmx-helper.c
+++ b/arch/powerpc/lib/vmx-helper.c
@@ -46,7 +46,7 @@ int exit_vmx_usercopy(void)
 	 * set and we are preemptible. The hack here is to schedule a
 	 * decrementer to fire here and reschedule for us if necessary.
 	 */
-	if (need_irq_preemption() && need_resched())
+	if (need_resched())
 		set_dec(1);
 	return 0;
 }
-- 
2.54.0

Re: [PATCH] powerpc: Remove dead non-preemption code

[Shrikanth Hegde]

Hi Christophe.

On 6/19/26 5:38 PM, Christophe Leroy (CS GROUP) wrote:
> Since commit 7dadeaa6e851 ("sched: Further restrict the preemption
> modes"), powerpc always has CONFIG_PREEMPTION because only
> CONFIG_PREEMPT and CONFIG_PREEMPT_LAZY are possible, even in
> dynamic preemption mode (see sched_dynamic_mode).
> 
> As a consequence, need_irq_preemption() is always true and can be
> removed.

right. this can be removed now.
Thanks for the cleanup.

> 
> And because commit bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY
> feature") includes linux/irq-entry-common.h which already declares
> sk_dynamic_irqentry_exit_cond_resched static key, asm/preempt.h
> becauses useless and can be removed.

s/becauses/becomes

> Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
> ---
>   arch/powerpc/include/asm/preempt.h | 16 ----------------
>   arch/powerpc/lib/vmx-helper.c      |  2 +-
>   2 files changed, 1 insertion(+), 17 deletions(-)
>   delete mode 100644 arch/powerpc/include/asm/preempt.h
> 
> diff --git a/arch/powerpc/include/asm/preempt.h b/arch/powerpc/include/asm/preempt.h
> deleted file mode 100644
> index 000e2b9681f3..000000000000
> --- a/arch/powerpc/include/asm/preempt.h
> +++ /dev/null
> @@ -1,16 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0 */
> -#ifndef __ASM_POWERPC_PREEMPT_H
> -#define __ASM_POWERPC_PREEMPT_H
> -
> -#include <asm-generic/preempt.h>
> -
> -#if defined(CONFIG_PREEMPT_DYNAMIC)
> -#include <linux/jump_label.h>
> -DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
> -#define need_irq_preemption() \
> -	(static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
> -#else
> -#define need_irq_preemption()   (IS_ENABLED(CONFIG_PREEMPTION))
> -#endif
> -
> -#endif /* __ASM_POWERPC_PREEMPT_H */
> diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c
> index 57e897b60db8..cc9fb72cb4eb 100644
> --- a/arch/powerpc/lib/vmx-helper.c
> +++ b/arch/powerpc/lib/vmx-helper.c
> @@ -46,7 +46,7 @@ int exit_vmx_usercopy(void)
>   	 * set and we are preemptible. The hack here is to schedule a
>   	 * decrementer to fire here and reschedule for us if necessary.
>   	 */
> -	if (need_irq_preemption() && need_resched())
> +	if (need_resched())
>   		set_dec(1);
>   	return 0;
>   }

I booted with the patch, still can change between lazy/full.
So,

Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>