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powerpc/smp: More generic support for "soft hotplug" 

This adds more generic support for doing CPU hotplug with a simple
idle loop and no actual reset of the processors. The generic
smp_generic_kick_cpu() does the hotplug bringup trick if the PACA
shows that the CPU has already been started at boot and we provide
an accessor for the CPU state.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2011-09-19 17:44:49 +00:00
parent b8bb922c68
commit fb82b83970
2 changed files with 26 additions and 5 deletions
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1
arch/powerpc/include/asm/smp.h
View File

@ -65,6 +65,7 @@ int generic_cpu_disable(void);
void generic_cpu_die(unsigned int cpu);
void generic_mach_cpu_die(void);
void generic_set_cpu_dead(unsigned int cpu);
int generic_check_cpu_restart(unsigned int cpu);
#endif
#ifdef CONFIG_PPC64

30
arch/powerpc/kernel/smp.c
View File

@ -70,6 +70,10 @@
static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);
#define get_idle_for_cpu(x) (per_cpu(idle_thread_array, x))
#define set_idle_for_cpu(x, p) (per_cpu(idle_thread_array, x) = (p))
/* State of each CPU during hotplug phases */
static DEFINE_PER_CPU(int, cpu_state) = { 0 };
#else
static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
#define get_idle_for_cpu(x) (idle_thread_array[(x)])
@ -104,12 +108,25 @@ int __devinit smp_generic_kick_cpu(int nr)
* cpu_start field to become non-zero After we set cpu_start,
* the processor will continue on to secondary_start
*/
paca[nr].cpu_start = 1;
smp_mb();
if (!paca[nr].cpu_start) {
paca[nr].cpu_start = 1;
smp_mb();
return 0;
}
#ifdef CONFIG_HOTPLUG_CPU
/*
* Ok it's not there, so it might be soft-unplugged, let's
* try to bring it back
*/
per_cpu(cpu_state, nr) = CPU_UP_PREPARE;
smp_wmb();
smp_send_reschedule(nr);
#endif /* CONFIG_HOTPLUG_CPU */
return 0;
}
#endif
#endif /* CONFIG_PPC64 */
static irqreturn_t call_function_action(int irq, void *data)
{
@ -357,8 +374,6 @@ void __devinit smp_prepare_boot_cpu(void)
}
#ifdef CONFIG_HOTPLUG_CPU
/* State of each CPU during hotplug phases */
static DEFINE_PER_CPU(int, cpu_state) = { 0 };
int generic_cpu_disable(void)
{
@ -406,6 +421,11 @@ void generic_set_cpu_dead(unsigned int cpu)
{
per_cpu(cpu_state, cpu) = CPU_DEAD;
}
int generic_check_cpu_restart(unsigned int cpu)
{
return per_cpu(cpu_state, cpu) == CPU_UP_PREPARE;
}
#endif
struct create_idle {