Messages in this thread Patch in this message | | | Date | Wed, 20 Nov 2019 11:09:11 +0000 | From | Sudeep Holla <> | Subject | Re: [PATCH] arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC |
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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
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