A quick poll of the ARM platforms that implement CPU Hotplug support shows that every platform treats CPU 0 as a special case that cannot be hotplugged. In fact every platform has identical code for platform_cpu_die which returns -EPERM in the case of CPU 0.
The user-facing sysfs interfaces should reflect this by not populating an 'online' entry for CPU 0 at all. This better reflects reality by making it clear to users that CPU 0 cannot be hotplugged.
This patch prevents CPU 0 from being marked as hotpluggable on all ARM platforms during CPU registration. This in turn prevents the creation of an 'online' sysfs interface for that CPU.
Signed-off-by: Mike Turquette mturquette@ti.com --- arch/arm/kernel/setup.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c index 70bca64..5f3f4bb 100644 --- a/arch/arm/kernel/setup.c +++ b/arch/arm/kernel/setup.c @@ -949,7 +949,8 @@ static int __init topology_init(void)
for_each_possible_cpu(cpu) { struct cpuinfo_arm *cpuinfo = &per_cpu(cpu_data, cpu); - cpuinfo->cpu.hotpluggable = 1; + if (cpu) + cpuinfo->cpu.hotpluggable = 1; register_cpu(&cpuinfo->cpu, cpu); }