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Commit fb82b839 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
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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: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent b8bb922c

arch/powerpc/include/asm/smp.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kernel/smp.c

+25 −5
Original line number Diff line number Diff line
@@ -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

	 */

	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 {