This branch is needed to allow preemptible IRQs to be scheduled,
otherwise the kernel hangs during boot on my e300 based platforms.
This branch is needed for both CONFIG_PREEMPT and CONFIG_PREEMPT_RT,
so broaden the check to CONFIG_PREEMPTION, which is selected by both.

This was previously set to CONFIG_PREEMPTION, but was reverted as part
of removing LAZY_PREEMPT support.

Fixes: b33022a48c79
Signed-off-by: Robert Joslyn <robert_joslyn@selinc.com>
---
 arch/powerpc/kernel/interrupt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index af62ec974b97..970039af8e92 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -396,7 +396,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
 		/* Returning to a kernel context with local irqs enabled. */
 		WARN_ON_ONCE(!(regs->msr & MSR_EE));
 again:
-		if (IS_ENABLED(CONFIG_PREEMPT)) {
+		if (IS_ENABLED(CONFIG_PREEMPTION)) {
 			/* Return to preemptible kernel context */
 			if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) {
 				if (preempt_count() == 0)
-- 
2.45.2

On 2024-12-26 11:12:38 [-0800], Robert Joslyn wrote:
> This branch is needed to allow preemptible IRQs to be scheduled,
> otherwise the kernel hangs during boot on my e300 based platforms.
> This branch is needed for both CONFIG_PREEMPT and CONFIG_PREEMPT_RT,
> so broaden the check to CONFIG_PREEMPTION, which is selected by both.
> 
> This was previously set to CONFIG_PREEMPTION, but was reverted as part
> of removing LAZY_PREEMPT support.

I remember I pointed this out while Shrikanth posted the preempt-lazy
patches but didn't realize that I need this in RT tree, too.

The lazy-preempt patches for powerpc were merged upstream, I am going to
pull them into the v6.6-series.
I am going to Cc you, hopefully you can confirm that it is working.

> Fixes: b33022a48c79
> Signed-off-by: Robert Joslyn <robert_joslyn@selinc.com>
> ---
>  arch/powerpc/kernel/interrupt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
> index af62ec974b97..970039af8e92 100644
> --- a/arch/powerpc/kernel/interrupt.c
> +++ b/arch/powerpc/kernel/interrupt.c
> @@ -396,7 +396,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
>  		/* Returning to a kernel context with local irqs enabled. */
>  		WARN_ON_ONCE(!(regs->msr & MSR_EE));
>  again:
> -		if (IS_ENABLED(CONFIG_PREEMPT)) {
> +		if (IS_ENABLED(CONFIG_PREEMPTION)) {
>  			/* Return to preemptible kernel context */
>  			if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) {
>  				if (preempt_count() == 0)

Sebastian

On 1/7/25 17:26, Sebastian Andrzej Siewior wrote:
> On 2024-12-26 11:12:38 [-0800], Robert Joslyn wrote:
>> This branch is needed to allow preemptible IRQs to be scheduled,
>> otherwise the kernel hangs during boot on my e300 based platforms.
>> This branch is needed for both CONFIG_PREEMPT and CONFIG_PREEMPT_RT,

Hi Robert.

Are you running with preempt=full or enabled preempt_rt ?
rt is yet to be supported on powerpc. are you having it enabled out of tree?

Also, I have sent out patch to enable dynamic preemption. It uses preempt_model_preemptible.
I think it should work for you as well. If you could give that a try and ensure it works, it would be great.
https://lore.kernel.org/all/20250106051919.55020-2-sshegde@linux.ibm.com/

>> so broaden the check to CONFIG_PREEMPTION, which is selected by both.
>>
>> This was previously set to CONFIG_PREEMPTION, but was reverted as part
>> of removing LAZY_PREEMPT support.
> 
> I remember I pointed this out while Shrikanth posted the preempt-lazy
> patches but didn't realize that I need this in RT tree, too.
> 
> The lazy-preempt patches for powerpc were merged upstream, I am going to
> pull them into the v6.6-series.
> I am going to Cc you, hopefully you can confirm that it is working.
> 
>> Fixes: b33022a48c79
>> Signed-off-by: Robert Joslyn <robert_joslyn@selinc.com>
>> ---
>>   arch/powerpc/kernel/interrupt.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
>> index af62ec974b97..970039af8e92 100644
>> --- a/arch/powerpc/kernel/interrupt.c
>> +++ b/arch/powerpc/kernel/interrupt.c
>> @@ -396,7 +396,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
>>   		/* Returning to a kernel context with local irqs enabled. */
>>   		WARN_ON_ONCE(!(regs->msr & MSR_EE));
>>   again:
>> -		if (IS_ENABLED(CONFIG_PREEMPT)) {
>> +		if (IS_ENABLED(CONFIG_PREEMPTION)) {
>>   			/* Return to preemptible kernel context */
>>   			if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) {
>>   				if (preempt_count() == 0)
> 
> Sebastian

On 2025-01-07 12:56:08 [+0100], To Robert Joslyn wrote:
> On 2024-12-26 11:12:38 [-0800], Robert Joslyn wrote:
> > This branch is needed to allow preemptible IRQs to be scheduled,
> > otherwise the kernel hangs during boot on my e300 based platforms.
> > This branch is needed for both CONFIG_PREEMPT and CONFIG_PREEMPT_RT,
> > so broaden the check to CONFIG_PREEMPTION, which is selected by both.
> > 
> > This was previously set to CONFIG_PREEMPTION, but was reverted as part
> > of removing LAZY_PREEMPT support.
> 
> I remember I pointed this out while Shrikanth posted the preempt-lazy
> patches but didn't realize that I need this in RT tree, too.
> 
> The lazy-preempt patches for powerpc were merged upstream, I am going to
> pull them into the v6.6-series.
> I am going to Cc you, hopefully you can confirm that it is working.

Robert, you are referring to v6.6-RT, correct?

Sebastian