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SubjectRe: [PATCH 03/27] smpboot: Define and use cpu_state per-cpu variable in generic code
On Fri, Jun 01, 2012 at 05:49:14PM +0530, Srivatsa S. Bhat wrote:
> Adding arch maintainers to Cc, which I had missed earlier. No changes to the
> patch.

Could someone explain what this variable does - afaics this patch adds
this per-cpu variable to all SMP architectures where its required or
not, and (so far) the generic code just writes one value to it.

Are there plans to make use of this in other generic code?

>
> =====
>
> 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
> Cc: Hirokazu Takata <takata@linux-m32r.org>
> Cc: Richard Kuo <rkuo@codeaurora.org>
> Cc: David Howells <dhowells@redhat.com>
> Cc: Bob Liu <lliubbo@gmail.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Richard Weinberger <richard@nod.at>
> Cc: Jesper Nilsson <jesper.nilsson@axis.com>
> Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Matt Turner <mattst88@gmail.com>
> 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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