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    SubjectRe: [PATCH 01/27] smpboot: Provide a generic method to boot secondary processors
    On Fri, Jun 01, 2012 at 05:39:27PM +0530, Srivatsa S. Bhat wrote:
    > +/* Implement the following functions in your architecture, as appropriate. */
    > +
    > +/**
    > + * __cpu_pre_starting()
    > + *
    > + * Implement whatever you need to do before the CPU_STARTING notifiers are
    > + * invoked. Note that the CPU_STARTING callbacks run *on* the cpu that is
    > + * coming up. So that cpu better be prepared! IOW, implement all the early
    > + * boot/init code for the cpu here. And do NOT enable interrupts.
    > + */
    > +#ifndef __cpu_pre_starting

    Why the ifndef?

    Thanks,
    Yong

    > +void __weak __cpu_pre_starting(void *arg) {}
    > +#endif
    > +
    > +/**
    > + * __cpu_pre_online()
    > + *
    > + * Implement whatever you need to do before the upcoming CPU is set in the
    > + * cpu_online_mask. (Setting the cpu in the cpu_online_mask is like an
    > + * announcement that the cpu has come up, because it would be publicly
    > + * visible now). Again, don't enable interrupts.
    > + */
    > +#ifndef __cpu_pre_online
    > +void __weak __cpu_pre_online(void *arg) {}
    > +#endif
    > +
    > +/**
    > + * __cpu_post_online()
    > + *
    > + * Implement whatever you need to do after the CPU has been set in the
    > + * cpu_online_mask, and before enabling interrupts and calling cpu_idle().
    > + * Ideally, it is preferable if you don't have anything to do here.
    > + * We want to move to a model where setting cpu_online_mask is pretty
    > + * much the final step. Again, don't enable interrupts.
    > + */
    > +#ifndef __cpu_post_online
    > +void __weak __cpu_post_online(void *arg) {}
    > +#endif
    > +
    > +
    > +/**
    > + * smpboot_start_secondary - Generic way to boot secondary processors
    > + */
    > +void __cpuinit smpboot_start_secondary(void *arg)
    > +{
    > + unsigned int cpu;
    > +
    > + /*
    > + * SMP booting is extremely fragile in some architectures. So run
    > + * the cpu initialization code first before anything else.
    > + */
    > + __cpu_pre_starting(arg);
    > +
    > + preempt_disable();
    > + cpu = smp_processor_id();
    > +
    > + /* Invoke the CPU_STARTING notifier callbacks */
    > + notify_cpu_starting(cpu);
    > +
    > + __cpu_pre_online(arg);
    > +
    > + /* Set the CPU in the cpu_online_mask */
    > + set_cpu_online(cpu, true);
    > +
    > + __cpu_post_online(arg);
    > +
    > + /* Enable local interrupts now */
    > + local_irq_enable();
    > +
    > + wmb();
    > + cpu_idle();
    > +
    > + /* We should never reach here! */
    > + BUG();
    > +}
    > diff --git a/kernel/smpboot.h b/kernel/smpboot.h
    > index 80c0acf..9753cc0 100644
    > --- a/kernel/smpboot.h
    > +++ b/kernel/smpboot.h
    > @@ -1,5 +1,5 @@
    > -#ifndef SMPBOOT_H
    > -#define SMPBOOT_H
    > +#ifndef __SMPBOOT_H
    > +#define __SMPBOOT_H
    >
    > struct task_struct;
    >
    >
    >
    > From: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    > Subject: [PATCH 02/27] smpboot: Add provisions for arch-specific locking around cpu_online_mask
    >
    > We want to make smp booting as generic as possible and remove code
    > duplication in arch/ directories.
    >
    > While manipulating the cpu_online_mask, x86 uses an additional lock, i.e.,
    > 'vector_lock'. So provide a generic way to implement such arch-specific
    > extra locking, by providing weakly defined functions arch_vector_lock()
    > and arch_vector_unlock() which can be overriden by different architectures
    > suitably.
    >
    > Cc: Thomas Gleixner <tglx@linutronix.de>
    > Cc: Suresh Siddha <suresh.b.siddha@intel.com>
    > Cc: Venkatesh Pallipadi <venki@google.com>
    > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    > ---
    >
    > kernel/smpboot.c | 11 ++++++++++-
    > 1 files changed, 10 insertions(+), 1 deletions(-)
    >
    > diff --git a/kernel/smpboot.c b/kernel/smpboot.c
    > index 6c26133..5ae1805 100644
    > --- a/kernel/smpboot.c
    > +++ b/kernel/smpboot.c
    > @@ -107,6 +107,13 @@ void __weak __cpu_pre_online(void *arg) {}
    > void __weak __cpu_post_online(void *arg) {}
    > #endif
    >
    > +/*
    > + * Optional arch-specific locking for manipulating cpu_online_mask while
    > + * bringing up secondary CPUs.
    > + */
    > +void __weak arch_vector_lock(void) {}
    > +void __weak arch_vector_unlock(void) {}
    > +
    >
    > /**
    > * smpboot_start_secondary - Generic way to boot secondary processors
    > @@ -129,8 +136,10 @@ void __cpuinit smpboot_start_secondary(void *arg)
    >
    > __cpu_pre_online(arg);
    >
    > - /* Set the CPU in the cpu_online_mask */
    > + /* Set the CPU in the cpu_online_mask with required locks held */
    > + arch_vector_lock();
    > set_cpu_online(cpu, true);
    > + arch_vector_unlock();
    >
    > __cpu_post_online(arg);
    >
    >
    >
    > From: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    > Subject: [PATCH 03/27] smpboot: Define and use cpu_state per-cpu variable in generic code
    >
    > The per-cpu variable cpu_state is used in x86 and also used in other
    > architectures, to track the state of the cpu during bringup and hotplug.
    > Pull it out into generic code.
    >
    > Cc: Tony Luck <tony.luck@intel.com>
    > Cc: Fenghua Yu <fenghua.yu@intel.com>
    > Cc: Ralf Baechle <ralf@linux-mips.org>
    > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    > Cc: Paul Mundt <lethal@linux-sh.org>
    > Cc: Chris Metcalf <cmetcalf@tilera.com>
    > Cc: Thomas Gleixner <tglx@linutronix.de>
    > Cc: Ingo Molnar <mingo@redhat.com>
    > Cc: "H. Peter Anvin" <hpa@zytor.com>
    > Cc: x86@kernel.org
    > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    > Cc: Jeremy Fitzhardinge <jeremy@goop.org>
    > Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    > Cc: Andrew Morton <akpm@linux-foundation.org>
    > Cc: Mike Frysinger <vapier@gentoo.org>
    > Cc: Yong Zhang <yong.zhang0@gmail.com>
    > Cc: Venkatesh Pallipadi <venki@google.com>
    > Cc: Suresh Siddha <suresh.b.siddha@intel.com>
    > Cc: linux-ia64@vger.kernel.org
    > Cc: linux-mips@linux-mips.org
    > Cc: linuxppc-dev@lists.ozlabs.org
    > Cc: linux-sh@vger.kernel.org
    > Cc: xen-devel@lists.xensource.com
    > Cc: virtualization@lists.linux-foundation.org
    > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    > ---
    >
    > arch/ia64/include/asm/cpu.h | 2 --
    > arch/ia64/kernel/process.c | 1 +
    > arch/ia64/kernel/smpboot.c | 6 +-----
    > arch/mips/cavium-octeon/smp.c | 4 +---
    > arch/powerpc/kernel/smp.c | 6 +-----
    > arch/sh/include/asm/smp.h | 2 --
    > arch/sh/kernel/smp.c | 4 +---
    > arch/tile/kernel/smpboot.c | 4 +---
    > arch/x86/include/asm/cpu.h | 2 --
    > arch/x86/kernel/smpboot.c | 4 +---
    > arch/x86/xen/smp.c | 1 +
    > include/linux/smpboot.h | 1 +
    > kernel/smpboot.c | 4 ++++
    > 13 files changed, 13 insertions(+), 28 deletions(-)
    >
    > diff --git a/arch/ia64/include/asm/cpu.h b/arch/ia64/include/asm/cpu.h
    > index fcca30b..1c3acac 100644
    > --- a/arch/ia64/include/asm/cpu.h
    > +++ b/arch/ia64/include/asm/cpu.h
    > @@ -12,8 +12,6 @@ struct ia64_cpu {
    >
    > DECLARE_PER_CPU(struct ia64_cpu, cpu_devices);
    >
    > -DECLARE_PER_CPU(int, cpu_state);
    > -
    > #ifdef CONFIG_HOTPLUG_CPU
    > extern int arch_register_cpu(int num);
    > extern void arch_unregister_cpu(int);
    > diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
    > index 5e0e86d..32566c7 100644
    > --- a/arch/ia64/kernel/process.c
    > +++ b/arch/ia64/kernel/process.c
    > @@ -29,6 +29,7 @@
    > #include <linux/kdebug.h>
    > #include <linux/utsname.h>
    > #include <linux/tracehook.h>
    > +#include <linux/smpboot.h>
    >
    > #include <asm/cpu.h>
    > #include <asm/delay.h>
    > diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c
    > index 963d2db..df00a3c 100644
    > --- a/arch/ia64/kernel/smpboot.c
    > +++ b/arch/ia64/kernel/smpboot.c
    > @@ -39,6 +39,7 @@
    > #include <linux/efi.h>
    > #include <linux/percpu.h>
    > #include <linux/bitops.h>
    > +#include <linux/smpboot.h>
    >
    > #include <linux/atomic.h>
    > #include <asm/cache.h>
    > @@ -111,11 +112,6 @@ extern unsigned long ia64_iobase;
    >
    > struct task_struct *task_for_booting_cpu;
    >
    > -/*
    > - * State for each CPU
    > - */
    > -DEFINE_PER_CPU(int, cpu_state);
    > -
    > cpumask_t cpu_core_map[NR_CPUS] __cacheline_aligned;
    > EXPORT_SYMBOL(cpu_core_map);
    > DEFINE_PER_CPU_SHARED_ALIGNED(cpumask_t, cpu_sibling_map);
    > diff --git a/arch/mips/cavium-octeon/smp.c b/arch/mips/cavium-octeon/smp.c
    > index 97e7ce9..93cd4b0 100644
    > --- a/arch/mips/cavium-octeon/smp.c
    > +++ b/arch/mips/cavium-octeon/smp.c
    > @@ -13,6 +13,7 @@
    > #include <linux/kernel_stat.h>
    > #include <linux/sched.h>
    > #include <linux/module.h>
    > +#include <linux/smpboot.h>
    >
    > #include <asm/mmu_context.h>
    > #include <asm/time.h>
    > @@ -252,9 +253,6 @@ static void octeon_cpus_done(void)
    >
    > #ifdef CONFIG_HOTPLUG_CPU
    >
    > -/* State of each CPU. */
    > -DEFINE_PER_CPU(int, cpu_state);
    > -
    > extern void fixup_irqs(void);
    >
    > static DEFINE_SPINLOCK(smp_reserve_lock);
    > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
    > index e1417c4..1928058a 100644
    > --- a/arch/powerpc/kernel/smp.c
    > +++ b/arch/powerpc/kernel/smp.c
    > @@ -31,6 +31,7 @@
    > #include <linux/cpu.h>
    > #include <linux/notifier.h>
    > #include <linux/topology.h>
    > +#include <linux/smpboot.h>
    >
    > #include <asm/ptrace.h>
    > #include <linux/atomic.h>
    > @@ -57,11 +58,6 @@
    > #define DBG(fmt...)
    > #endif
    >
    > -#ifdef CONFIG_HOTPLUG_CPU
    > -/* State of each CPU during hotplug phases */
    > -static DEFINE_PER_CPU(int, cpu_state) = { 0 };
    > -#endif
    > -
    > struct thread_info *secondary_ti;
    >
    > DEFINE_PER_CPU(cpumask_var_t, cpu_sibling_map);
    > diff --git a/arch/sh/include/asm/smp.h b/arch/sh/include/asm/smp.h
    > index 78b0d0f4..bda041e 100644
    > --- a/arch/sh/include/asm/smp.h
    > +++ b/arch/sh/include/asm/smp.h
    > @@ -31,8 +31,6 @@ enum {
    > SMP_MSG_NR, /* must be last */
    > };
    >
    > -DECLARE_PER_CPU(int, cpu_state);
    > -
    > void smp_message_recv(unsigned int msg);
    > void smp_timer_broadcast(const struct cpumask *mask);
    >
    > diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
    > index b86e9ca..8e0fde0 100644
    > --- a/arch/sh/kernel/smp.c
    > +++ b/arch/sh/kernel/smp.c
    > @@ -22,6 +22,7 @@
    > #include <linux/interrupt.h>
    > #include <linux/sched.h>
    > #include <linux/atomic.h>
    > +#include <linux/smpboot.h>
    > #include <asm/processor.h>
    > #include <asm/mmu_context.h>
    > #include <asm/smp.h>
    > @@ -34,9 +35,6 @@ int __cpu_logical_map[NR_CPUS]; /* Map logical to physical */
    >
    > struct plat_smp_ops *mp_ops = NULL;
    >
    > -/* State of each CPU */
    > -DEFINE_PER_CPU(int, cpu_state) = { 0 };
    > -
    > void __cpuinit register_smp_ops(struct plat_smp_ops *ops)
    > {
    > if (mp_ops)
    > diff --git a/arch/tile/kernel/smpboot.c b/arch/tile/kernel/smpboot.c
    > index e686c5a..24a9c06 100644
    > --- a/arch/tile/kernel/smpboot.c
    > +++ b/arch/tile/kernel/smpboot.c
    > @@ -25,13 +25,11 @@
    > #include <linux/delay.h>
    > #include <linux/err.h>
    > #include <linux/irq.h>
    > +#include <linux/smpboot.h>
    > #include <asm/mmu_context.h>
    > #include <asm/tlbflush.h>
    > #include <asm/sections.h>
    >
    > -/* State of each CPU. */
    > -static DEFINE_PER_CPU(int, cpu_state) = { 0 };
    > -
    > /* The messaging code jumps to this pointer during boot-up */
    > unsigned long start_cpu_function_addr;
    >
    > diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
    > index 4564c8e..2d0b239 100644
    > --- a/arch/x86/include/asm/cpu.h
    > +++ b/arch/x86/include/asm/cpu.h
    > @@ -30,8 +30,6 @@ extern int arch_register_cpu(int num);
    > extern void arch_unregister_cpu(int);
    > #endif
    >
    > -DECLARE_PER_CPU(int, cpu_state);
    > -
    > int mwait_usable(const struct cpuinfo_x86 *);
    >
    > #endif /* _ASM_X86_CPU_H */
    > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
    > index bfbe30e..269bc1f 100644
    > --- a/arch/x86/kernel/smpboot.c
    > +++ b/arch/x86/kernel/smpboot.c
    > @@ -51,6 +51,7 @@
    > #include <linux/stackprotector.h>
    > #include <linux/gfp.h>
    > #include <linux/cpuidle.h>
    > +#include <linux/smpboot.h>
    >
    > #include <asm/acpi.h>
    > #include <asm/desc.h>
    > @@ -73,9 +74,6 @@
    > #include <asm/smpboot_hooks.h>
    > #include <asm/i8259.h>
    >
    > -/* State of each CPU */
    > -DEFINE_PER_CPU(int, cpu_state) = { 0 };
    > -
    > #ifdef CONFIG_HOTPLUG_CPU
    > /*
    > * We need this for trampoline_base protection from concurrent accesses when
    > diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
    > index 2ef5948..09a7199 100644
    > --- a/arch/x86/xen/smp.c
    > +++ b/arch/x86/xen/smp.c
    > @@ -16,6 +16,7 @@
    > #include <linux/err.h>
    > #include <linux/slab.h>
    > #include <linux/smp.h>
    > +#include <linux/smpboot.h>
    >
    > #include <asm/paravirt.h>
    > #include <asm/desc.h>
    > diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h
    > index 63bbedd..834d90c 100644
    > --- a/include/linux/smpboot.h
    > +++ b/include/linux/smpboot.h
    > @@ -5,6 +5,7 @@
    > #ifndef SMPBOOT_H
    > #define SMPBOOT_H
    >
    > +DECLARE_PER_CPU(int, cpu_state);
    > extern void smpboot_start_secondary(void *arg);
    >
    > #endif
    > diff --git a/kernel/smpboot.c b/kernel/smpboot.c
    > index 5ae1805..0df43b0 100644
    > --- a/kernel/smpboot.c
    > +++ b/kernel/smpboot.c
    > @@ -67,6 +67,8 @@ void __init idle_threads_init(void)
    > }
    > #endif
    >
    > +/* State of each CPU during bringup/teardown */
    > +DEFINE_PER_CPU(int, cpu_state) = { 0 };
    >
    > /* Implement the following functions in your architecture, as appropriate. */
    >
    > @@ -141,6 +143,8 @@ void __cpuinit smpboot_start_secondary(void *arg)
    > set_cpu_online(cpu, true);
    > arch_vector_unlock();
    >
    > + per_cpu(cpu_state, cpu) = CPU_ONLINE;
    > +
    > __cpu_post_online(arg);
    >
    > /* Enable local interrupts now */
    >
    >
    > --
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