[PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

[PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

[Dietmar Eggemann]

Commit ca74b316df96 ("arm: Use common cpu_topology structure and
functions.") changed cpu_coregroup_mask() from the ARM32 specific
implementation in arch/arm/include/asm/topology.h to the one shared
with ARM64 and RISCV in drivers/base/arch_topology.c.

Currently on Arm32 (TC2 w/ CONFIG_SCHED_MC) the task scheduler setup
code (w/ CONFIG_SCHED_DEBUG) shows this during CPU hotplug:

  ERROR: groups don't span domain->span

It happens to CPUs of the cluster of the CPU which gets hot-plugged
out on scheduler domain MC.

Turns out that the shared cpu_coregroup_mask() requires that the
hot-plugged CPU is removed from the core_sibling mask via
remove_cpu_topology(). Otherwise the 'is core_sibling subset of
cpumask_of_node()' doesn't work. In this case the task scheduler has to
deal with cpumask_of_node instead of core_sibling which is wrong on
scheduler domain MC.

e.g. CPU3 hot-plugged out on TC2 [cluster0: 0,3-4 cluster1: 1-2]:

  cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,3-4
                                                                  ^
should be:

  cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,4

Add remove_cpu_topology() to __cpu_disable() to remove the CPU from the
topology masks in case of a CPU hotplug out operation.

At the same time tweak store_cpu_topology() slightly so it will call
update_siblings_masks() in case of CPU hotplug in operation via
secondary_start_kernel()->smp_store_cpu_info().

This aligns the Arm32 implementation with the Arm64 one.

Fixes: ca74b316df96 ("arm: Use common cpu_topology structure and functions")
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
---
 arch/arm/kernel/smp.c      |  2 ++
 arch/arm/kernel/topology.c | 15 +++++++--------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 4b0bab2607e4..139c0d98fa29 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -240,6 +240,8 @@ int __cpu_disable(void)
 	if (ret)
 		return ret;
 
+	remove_cpu_topology(cpu);
+
 	/*
 	 * Take this CPU offline.  Once we clear this, we can't return,
 	 * and we must not schedule until we're ready to give up the cpu.
diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index 5b9faba03afb..b37b0a340991 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -196,9 +196,8 @@ void store_cpu_topology(unsigned int cpuid)
 	struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
 	unsigned int mpidr;
 
-	/* If the cpu topology has been already set, just return */
-	if (cpuid_topo->core_id != -1)
-		return;
+	if (cpuid_topo->package_id != -1)
+		goto topology_populated;
 
 	mpidr = read_cpuid_mpidr();
 
@@ -231,14 +230,14 @@ void store_cpu_topology(unsigned int cpuid)
 		cpuid_topo->package_id = -1;
 	}
 
-	update_siblings_masks(cpuid);
-
 	update_cpu_capacity(cpuid);
 
 	pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
-		cpuid, cpu_topology[cpuid].thread_id,
-		cpu_topology[cpuid].core_id,
-		cpu_topology[cpuid].package_id, mpidr);
+		cpuid, cpuid_topo->thread_id, cpuid_topo->core_id,
+		cpuid_topo->package_id, mpidr);
+
+topology_populated:
+	update_siblings_masks(cpuid);
 }
 
 static inline int cpu_corepower_flags(void)
-- 
2.17.1

Re: [PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

[Sudeep Holla]

Hi Dietmar, Lukasz,

Thanks for digging this bug and fixing it.

On Wed, Nov 20, 2019 at 10:42:12AM +0000, Dietmar Eggemann wrote:
> Commit ca74b316df96 ("arm: Use common cpu_topology structure and
> functions.") changed cpu_coregroup_mask() from the ARM32 specific
> implementation in arch/arm/include/asm/topology.h to the one shared
> with ARM64 and RISCV in drivers/base/arch_topology.c.
>
> Currently on Arm32 (TC2 w/ CONFIG_SCHED_MC) the task scheduler setup
> code (w/ CONFIG_SCHED_DEBUG) shows this during CPU hotplug:
>
>   ERROR: groups don't span domain->span
>
> It happens to CPUs of the cluster of the CPU which gets hot-plugged
> out on scheduler domain MC.
>
> Turns out that the shared cpu_coregroup_mask() requires that the
> hot-plugged CPU is removed from the core_sibling mask via
> remove_cpu_topology(). Otherwise the 'is core_sibling subset of
> cpumask_of_node()' doesn't work. In this case the task scheduler has to
> deal with cpumask_of_node instead of core_sibling which is wrong on
> scheduler domain MC.
>
> e.g. CPU3 hot-plugged out on TC2 [cluster0: 0,3-4 cluster1: 1-2]:
>
>   cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,3-4
>                                                                   ^
> should be:
>
>   cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,4
>
> Add remove_cpu_topology() to __cpu_disable() to remove the CPU from the
> topology masks in case of a CPU hotplug out operation.
>
> At the same time tweak store_cpu_topology() slightly so it will call
> update_siblings_masks() in case of CPU hotplug in operation via
> secondary_start_kernel()->smp_store_cpu_info().
>
> This aligns the Arm32 implementation with the Arm64 one.
>
> Fixes: ca74b316df96 ("arm: Use common cpu_topology structure and functions")

Apart from the minor nit below,

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>

> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> ---
>  arch/arm/kernel/smp.c      |  2 ++
>  arch/arm/kernel/topology.c | 15 +++++++--------
>  2 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 4b0bab2607e4..139c0d98fa29 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -240,6 +240,8 @@ int __cpu_disable(void)
>  	if (ret)
>  		return ret;
>
> +	remove_cpu_topology(cpu);
> +
>  	/*
>  	 * Take this CPU offline.  Once we clear this, we can't return,
>  	 * and we must not schedule until we're ready to give up the cpu.
> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
> index 5b9faba03afb..b37b0a340991 100644
> --- a/arch/arm/kernel/topology.c
> +++ b/arch/arm/kernel/topology.c
> @@ -196,9 +196,8 @@ void store_cpu_topology(unsigned int cpuid)
>  	struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
>  	unsigned int mpidr;
>
> -	/* If the cpu topology has been already set, just return */
> -	if (cpuid_topo->core_id != -1)
> -		return;
> +	if (cpuid_topo->package_id != -1)
> +		goto topology_populated;
>
>  	mpidr = read_cpuid_mpidr();
>
> @@ -231,14 +230,14 @@ void store_cpu_topology(unsigned int cpuid)
>  		cpuid_topo->package_id = -1;
>  	}
>
> -	update_siblings_masks(cpuid);
> -
>  	update_cpu_capacity(cpuid);
>
>  	pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
> -		cpuid, cpu_topology[cpuid].thread_id,
> -		cpu_topology[cpuid].core_id,
> -		cpu_topology[cpuid].package_id, mpidr);
> +		cpuid, cpuid_topo->thread_id, cpuid_topo->core_id,
> +		cpuid_topo->package_id, mpidr);
> +

[nit] The above is a clearly cosmetic cleanup and shouldn't be part of
this fix as they will be backported automatically. So I prefer to drop
this or make it separate patch if required.

--
Regards,
Sudeep

Re: [PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

[Lukasz Luba]

Hi Dietmar,

On 11/20/19 10:42 AM, Dietmar Eggemann wrote:
> Commit ca74b316df96 ("arm: Use common cpu_topology structure and
> functions.") changed cpu_coregroup_mask() from the ARM32 specific
> implementation in arch/arm/include/asm/topology.h to the one shared
> with ARM64 and RISCV in drivers/base/arch_topology.c.
> 
> Currently on Arm32 (TC2 w/ CONFIG_SCHED_MC) the task scheduler setup
> code (w/ CONFIG_SCHED_DEBUG) shows this during CPU hotplug:
> 
>    ERROR: groups don't span domain->span
> 
> It happens to CPUs of the cluster of the CPU which gets hot-plugged
> out on scheduler domain MC.
> 
> Turns out that the shared cpu_coregroup_mask() requires that the
> hot-plugged CPU is removed from the core_sibling mask via
> remove_cpu_topology(). Otherwise the 'is core_sibling subset of
> cpumask_of_node()' doesn't work. In this case the task scheduler has to
> deal with cpumask_of_node instead of core_sibling which is wrong on
> scheduler domain MC.
> 
> e.g. CPU3 hot-plugged out on TC2 [cluster0: 0,3-4 cluster1: 1-2]:
> 
>    cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,3-4
>                                                                    ^
> should be:
> 
>    cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,4
> 
> Add remove_cpu_topology() to __cpu_disable() to remove the CPU from the
> topology masks in case of a CPU hotplug out operation.
> 
> At the same time tweak store_cpu_topology() slightly so it will call
> update_siblings_masks() in case of CPU hotplug in operation via
> secondary_start_kernel()->smp_store_cpu_info().
> 
> This aligns the Arm32 implementation with the Arm64 one.

Looks good to me.

Tested-and-Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>

> 
> Fixes: ca74b316df96 ("arm: Use common cpu_topology structure and functions")
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> ---
>   arch/arm/kernel/smp.c      |  2 ++
>   arch/arm/kernel/topology.c | 15 +++++++--------
>   2 files changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 4b0bab2607e4..139c0d98fa29 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -240,6 +240,8 @@ int __cpu_disable(void)
>   	if (ret)
>   		return ret;
>   
> +	remove_cpu_topology(cpu);
> +
>   	/*
>   	 * Take this CPU offline.  Once we clear this, we can't return,
>   	 * and we must not schedule until we're ready to give up the cpu.
> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
> index 5b9faba03afb..b37b0a340991 100644
> --- a/arch/arm/kernel/topology.c
> +++ b/arch/arm/kernel/topology.c
> @@ -196,9 +196,8 @@ void store_cpu_topology(unsigned int cpuid)
>   	struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
>   	unsigned int mpidr;
>   
> -	/* If the cpu topology has been already set, just return */
> -	if (cpuid_topo->core_id != -1)
> -		return;
> +	if (cpuid_topo->package_id != -1)
> +		goto topology_populated;
>   
>   	mpidr = read_cpuid_mpidr();
>   
> @@ -231,14 +230,14 @@ void store_cpu_topology(unsigned int cpuid)
>   		cpuid_topo->package_id = -1;
>   	}
>   
> -	update_siblings_masks(cpuid);
> -
>   	update_cpu_capacity(cpuid);
>   
>   	pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
> -		cpuid, cpu_topology[cpuid].thread_id,
> -		cpu_topology[cpuid].core_id,
> -		cpu_topology[cpuid].package_id, mpidr);
> +		cpuid, cpuid_topo->thread_id, cpuid_topo->core_id,
> +		cpuid_topo->package_id, mpidr);
> +
> +topology_populated:
> +	update_siblings_masks(cpuid);
>   }
>   
>   static inline int cpu_corepower_flags(void)
> 

Re: [PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

[Dietmar Eggemann]

On 20.11.19 11:09, Sudeep Holla wrote:
> Hi Dietmar, Lukasz,
> 
> Thanks for digging this bug and fixing it.
> 
> On Wed, Nov 20, 2019 at 10:42:12AM +0000, Dietmar Eggemann wrote:

[...]

>> @@ -231,14 +230,14 @@ void store_cpu_topology(unsigned int cpuid)
>>  		cpuid_topo->package_id = -1;
>>  	}
>>
>> -	update_siblings_masks(cpuid);
>> -
>>  	update_cpu_capacity(cpuid);
>>
>>  	pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
>> -		cpuid, cpu_topology[cpuid].thread_id,
>> -		cpu_topology[cpuid].core_id,
>> -		cpu_topology[cpuid].package_id, mpidr);
>> +		cpuid, cpuid_topo->thread_id, cpuid_topo->core_id,
>> +		cpuid_topo->package_id, mpidr);
>> +
> 
> [nit] The above is a clearly cosmetic cleanup and shouldn't be part of
> this fix as they will be backported automatically. So I prefer to drop
> this or make it separate patch if required.

I can get rid of this cleanup in v2. Thanks for the review!

Re: [PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

[Ondřej Jirman]

Hello,

On Wed, Nov 20, 2019 at 10:42:12AM +0000, Dietmar Eggemann wrote:
> Commit ca74b316df96 ("arm: Use common cpu_topology structure and
> functions.") changed cpu_coregroup_mask() from the ARM32 specific
> implementation in arch/arm/include/asm/topology.h to the one shared
> with ARM64 and RISCV in drivers/base/arch_topology.c.
> 
> Currently on Arm32 (TC2 w/ CONFIG_SCHED_MC) the task scheduler setup
> code (w/ CONFIG_SCHED_DEBUG) shows this during CPU hotplug:
> 
>   ERROR: groups don't span domain->span
> 
> It happens to CPUs of the cluster of the CPU which gets hot-plugged
> out on scheduler domain MC.
> 
> Turns out that the shared cpu_coregroup_mask() requires that the
> hot-plugged CPU is removed from the core_sibling mask via
> remove_cpu_topology(). Otherwise the 'is core_sibling subset of
> cpumask_of_node()' doesn't work. In this case the task scheduler has to
> deal with cpumask_of_node instead of core_sibling which is wrong on
> scheduler domain MC.
> 
> e.g. CPU3 hot-plugged out on TC2 [cluster0: 0,3-4 cluster1: 1-2]:
> 
>   cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,3-4
>                                                                   ^
> should be:
> 
>   cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,4
> 
> Add remove_cpu_topology() to __cpu_disable() to remove the CPU from the
> topology masks in case of a CPU hotplug out operation.
> 
> At the same time tweak store_cpu_topology() slightly so it will call
> update_siblings_masks() in case of CPU hotplug in operation via
> secondary_start_kernel()->smp_store_cpu_info().
> 
> This aligns the Arm32 implementation with the Arm64 one.
> 
> Fixes: ca74b316df96 ("arm: Use common cpu_topology structure and functions")
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

This fixes CPU hotplug and correspondent suspend to ram/resume failures (that
disables and re-enables non-boot CPUs) on A83T SoC, that I've seen since
5.4-rc1.

Tested-by: Ondrej Jirman <megous@megous.com>

thanks,
	o.

> ---
>  arch/arm/kernel/smp.c      |  2 ++
>  arch/arm/kernel/topology.c | 15 +++++++--------
>  2 files changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 4b0bab2607e4..139c0d98fa29 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -240,6 +240,8 @@ int __cpu_disable(void)
>  	if (ret)
>  		return ret;
>  
> +	remove_cpu_topology(cpu);
> +
>  	/*
>  	 * Take this CPU offline.  Once we clear this, we can't return,
>  	 * and we must not schedule until we're ready to give up the cpu.
> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
> index 5b9faba03afb..b37b0a340991 100644
> --- a/arch/arm/kernel/topology.c
> +++ b/arch/arm/kernel/topology.c
> @@ -196,9 +196,8 @@ void store_cpu_topology(unsigned int cpuid)
>  	struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
>  	unsigned int mpidr;
>  
> -	/* If the cpu topology has been already set, just return */
> -	if (cpuid_topo->core_id != -1)
> -		return;
> +	if (cpuid_topo->package_id != -1)
> +		goto topology_populated;
>  
>  	mpidr = read_cpuid_mpidr();
>  
> @@ -231,14 +230,14 @@ void store_cpu_topology(unsigned int cpuid)
>  		cpuid_topo->package_id = -1;
>  	}
>  
> -	update_siblings_masks(cpuid);
> -
>  	update_cpu_capacity(cpuid);
>  
>  	pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
> -		cpuid, cpu_topology[cpuid].thread_id,
> -		cpu_topology[cpuid].core_id,
> -		cpu_topology[cpuid].package_id, mpidr);
> +		cpuid, cpuid_topo->thread_id, cpuid_topo->core_id,
> +		cpuid_topo->package_id, mpidr);
> +
> +topology_populated:
> +	update_siblings_masks(cpuid);
>  }
>  
>  static inline int cpu_corepower_flags(void)
> -- 
> 2.17.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

[Dietmar Eggemann]

On 24/11/2019 22:47, Ondřej Jirman wrote:
> Hello,
> 
> On Wed, Nov 20, 2019 at 10:42:12AM +0000, Dietmar Eggemann wrote:

[...]

>> Fixes: ca74b316df96 ("arm: Use common cpu_topology structure and functions")
>> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> 
> This fixes CPU hotplug and correspondent suspend to ram/resume failures (that
> disables and re-enables non-boot CPUs) on A83T SoC, that I've seen since
> 5.4-rc1.
> 
> Tested-by: Ondrej Jirman <megous@megous.com>

Thanks for testing! Which Cpufreq driver is your system using?

[...]

Re: [PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

[Ondřej Jirman]

On Tue, Nov 26, 2019 at 11:42:02AM +0100, Dietmar Eggemann wrote:
> On 24/11/2019 22:47, Ondřej Jirman wrote:
> > Hello,
> > 
> > On Wed, Nov 20, 2019 at 10:42:12AM +0000, Dietmar Eggemann wrote:
> 
> [...]
> 
> >> Fixes: ca74b316df96 ("arm: Use common cpu_topology structure and functions")
> >> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> > 
> > This fixes CPU hotplug and correspondent suspend to ram/resume failures (that
> > disables and re-enables non-boot CPUs) on A83T SoC, that I've seen since
> > 5.4-rc1.
> > 
> > Tested-by: Ondrej Jirman <megous@megous.com>
> 
> Thanks for testing! Which Cpufreq driver is your system using?

Hello,

it's using cpufreq-dt.

regards,
	o.

> [...]
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

[Dietmar Eggemann]

On 26/11/2019 22:45, Ondřej Jirman wrote:
> On Tue, Nov 26, 2019 at 11:42:02AM +0100, Dietmar Eggemann wrote:
>> On 24/11/2019 22:47, Ondřej Jirman wrote:
>>> Hello,
>>>
>>> On Wed, Nov 20, 2019 at 10:42:12AM +0000, Dietmar Eggemann wrote:

[...]

>> Thanks for testing! Which Cpufreq driver is your system using?
> 
> Hello,
> 
> it's using cpufreq-dt.

Thanks for the info! It's dt-based so this one is safe in regards to
retrieving the correct topology core mask during CPU hp stress (i.e.
from multiple CPUs at the same time).

[...]