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Commit f3705136 authored by Zwane Mwaikambo's avatar Zwane Mwaikambo Committed by Linus Torvalds
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[PATCH] i386 CPU hotplug 



(The i386 CPU hotplug patch provides infrastructure for some work which Pavel
is doing as well as for ACPI S3 (suspend-to-RAM) work which Li Shaohua
<shaohua.li@intel.com> is doing)

The following provides i386 architecture support for safely unregistering and
registering processors during runtime, updated for the current -mm tree.  In
order to avoid dumping cpu hotplug code into kernel/irq/* i dropped the
cpu_online check in do_IRQ() by modifying fixup_irqs().  The difference being
that on cpu offline, fixup_irqs() is called before we clear the cpu from
cpu_online_map and a long delay in order to ensure that we never have any
queued external interrupts on the APICs.  There are additional changes to s390
and ppc64 to account for this change.

1) Add CONFIG_HOTPLUG_CPU
2) disable local APIC timer on dead cpus.
3) Disable preempt around irq balancing to prevent CPUs going down.
4) Print irq stats for all possible cpus.
5) Debugging check for interrupts on offline cpus.
6) Hacky fixup_irqs() to redirect irqs when cpus go off/online.
7) play_dead() for offline cpus to spin inside.
8) Handle offline cpus set in flush_tlb_others().
9) Grab lock earlier in smp_call_function() to prevent CPUs going down.
10) Implement __cpu_disable() and __cpu_die().
11) Enable local interrupts in cpu_enable() after fixup_irqs()
12) Don't fiddle with NMI on dead cpu, but leave intact on other cpus.
13) Program IRQ affinity whilst cpu is still in cpu_online_map on offline.

Signed-off-by: default avatarZwane Mwaikambo <zwane@linuxpower.ca>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent d92de65c

arch/i386/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -1250,6 +1250,15 @@ config SCx200 
	  This support is also available as a module.  If compiled as a

	  module, it will be called scx200.



config HOTPLUG_CPU

	bool "Support for hot-pluggable CPUs (EXPERIMENTAL)"

	depends on SMP && HOTPLUG && EXPERIMENTAL

	---help---

	  Say Y here to experiment with turning CPUs off and on.  CPUs

	  can be controlled through /sys/devices/system/cpu.



	  Say N.



source "drivers/pcmcia/Kconfig"



source "drivers/pci/hotplug/Kconfig"

arch/i386/kernel/apic.c

+2 −1
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 
#include <linux/mc146818rtc.h>

#include <linux/kernel_stat.h>

#include <linux/sysdev.h>

#include <linux/cpu.h>



#include <asm/atomic.h>

#include <asm/smp.h>
@@ -1048,7 +1049,7 @@ void __init setup_secondary_APIC_clock(void) 
	setup_APIC_timer(calibration_result);

}



void __init disable_APIC_timer(void)

void __devinit disable_APIC_timer(void)

{

	if (using_apic_timer) {

		unsigned long v;

arch/i386/kernel/io_apic.c

+2 −0
Original line number Diff line number Diff line
@@ -576,9 +576,11 @@ static int balanced_irq(void *unused) 
		try_to_freeze(PF_FREEZE);

		if (time_after(jiffies,

				prev_balance_time+balanced_irq_interval)) {

			preempt_disable();

			do_irq_balance();

			prev_balance_time = jiffies;

			time_remaining = balanced_irq_interval;

			preempt_enable();

		}

	}

	return 0;

arch/i386/kernel/irq.c

+54 −13
Original line number Diff line number Diff line
@@ -15,6 +15,9 @@ 
#include <linux/seq_file.h>

#include <linux/interrupt.h>

#include <linux/kernel_stat.h>

#include <linux/notifier.h>

#include <linux/cpu.h>

#include <linux/delay.h>



DEFINE_PER_CPU(irq_cpustat_t, irq_stat) ____cacheline_maxaligned_in_smp;

EXPORT_PER_CPU_SYMBOL(irq_stat);
@@ -210,8 +213,7 @@ int show_interrupts(struct seq_file *p, void *v) 


	if (i == 0) {

		seq_printf(p, "           ");

		for (j=0; j<NR_CPUS; j++)

			if (cpu_online(j))

		for_each_cpu(j)

			seq_printf(p, "CPU%d       ",j);

		seq_putc(p, '\n');

	}
@@ -225,8 +227,7 @@ int show_interrupts(struct seq_file *p, void *v) 
#ifndef CONFIG_SMP

		seq_printf(p, "%10u ", kstat_irqs(i));

#else

		for (j = 0; j < NR_CPUS; j++)

			if (cpu_online(j))

		for_each_cpu(j)

			seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);

#endif

		seq_printf(p, " %14s", irq_desc[i].handler->typename);
@@ -240,14 +241,12 @@ int show_interrupts(struct seq_file *p, void *v) 
		spin_unlock_irqrestore(&irq_desc[i].lock, flags);

	} else if (i == NR_IRQS) {

		seq_printf(p, "NMI: ");

		for (j = 0; j < NR_CPUS; j++)

			if (cpu_online(j))

		for_each_cpu(j)

			seq_printf(p, "%10u ", nmi_count(j));

		seq_putc(p, '\n');

#ifdef CONFIG_X86_LOCAL_APIC

		seq_printf(p, "LOC: ");

		for (j = 0; j < NR_CPUS; j++)

			if (cpu_online(j))

		for_each_cpu(j)

			seq_printf(p, "%10u ",

				per_cpu(irq_stat,j).apic_timer_irqs);

		seq_putc(p, '\n');
@@ -259,3 +258,45 @@ int show_interrupts(struct seq_file *p, void *v) 
	}

	return 0;

}



#ifdef CONFIG_HOTPLUG_CPU

#include <mach_apic.h>



void fixup_irqs(cpumask_t map)

{

	unsigned int irq;

	static int warned;



	for (irq = 0; irq < NR_IRQS; irq++) {

		cpumask_t mask;

		if (irq == 2)

			continue;



		cpus_and(mask, irq_affinity[irq], map);

		if (any_online_cpu(mask) == NR_CPUS) {

			printk("Breaking affinity for irq %i\n", irq);

			mask = map;

		}

		if (irq_desc[irq].handler->set_affinity)

			irq_desc[irq].handler->set_affinity(irq, mask);

		else if (irq_desc[irq].action && !(warned++))

			printk("Cannot set affinity for irq %i\n", irq);

	}



#if 0

	barrier();

	/* Ingo Molnar says: "after the IO-APIC masks have been redirected

	   [note the nop - the interrupt-enable boundary on x86 is two

	   instructions from sti] - to flush out pending hardirqs and

	   IPIs. After this point nothing is supposed to reach this CPU." */

	__asm__ __volatile__("sti; nop; cli");

	barrier();

#else

	/* That doesn't seem sufficient.  Give it 1ms. */

	local_irq_enable();

	mdelay(1);

	local_irq_disable();

#endif

}

#endif

arch/i386/kernel/process.c

+38 −1
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 


#include <stdarg.h>



#include <linux/cpu.h>

#include <linux/errno.h>

#include <linux/sched.h>

#include <linux/fs.h>
@@ -55,6 +56,9 @@ 
#include <linux/irq.h>

#include <linux/err.h>



#include <asm/tlbflush.h>

#include <asm/cpu.h>



asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");



static int hlt_counter;
@@ -143,6 +147,34 @@ static void poll_idle (void) 
	}

}



#ifdef CONFIG_HOTPLUG_CPU

#include <asm/nmi.h>

/* We don't actually take CPU down, just spin without interrupts. */

static inline void play_dead(void)

{

	/* Ack it */

	__get_cpu_var(cpu_state) = CPU_DEAD;



	/* We shouldn't have to disable interrupts while dead, but

	 * some interrupts just don't seem to go away, and this makes

	 * it "work" for testing purposes. */

	/* Death loop */

	while (__get_cpu_var(cpu_state) != CPU_UP_PREPARE)

		cpu_relax();



	local_irq_disable();

	__flush_tlb_all();

	cpu_set(smp_processor_id(), cpu_online_map);

	enable_APIC_timer();

	local_irq_enable();

}

#else

static inline void play_dead(void)

{

	BUG();

}

#endif /* CONFIG_HOTPLUG_CPU */



/*

 * The idle thread. There's no useful work to be

 * done, so just try to conserve power and have a
@@ -151,6 +183,8 @@ static void poll_idle (void) 
 */

void cpu_idle(void)

{

	int cpu = raw_smp_processor_id();



	/* endless idle loop with no priority at all */

	while (1) {

		while (!need_resched()) {
@@ -165,6 +199,9 @@ void cpu_idle (void) 
			if (!idle)

				idle = default_idle;



			if (cpu_is_offline(cpu))

				play_dead();



			__get_cpu_var(irq_stat).idle_timestamp = jiffies;

			idle();

		}