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    Subject[tip:x86/irq] x86, 32-bit: Align percpu area and irq stacks to THREAD_SIZE
    Commit-ID:  fe8e0c25cad28e8858ecfa5863333c70685a6811
    Gitweb: http://git.kernel.org/tip/fe8e0c25cad28e8858ecfa5863333c70685a6811
    Author: Alexander van Heukelum <heukelum@fastmail.fm>
    AuthorDate: Mon, 6 Sep 2010 20:53:42 +0200
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Tue, 7 Sep 2010 05:07:00 +0200

    x86, 32-bit: Align percpu area and irq stacks to THREAD_SIZE

    The irq stacks, located in the percpu-area, need to be
    THREAD_SIZE aligned. Add the infrastucture to align percpu
    variables to larger-than-pagesize amounts within the percpu
    area, and use it to specify the alignment for the irq stacks.
    Also align the percpu area itself to THREAD_SIZE.

    This should make irq stacks work with 8K THREAD_SIZE.

    Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: hch@lst.de
    LKML-Reference: <1283799222.15941.1393621887@webmail.messagingengine.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    arch/x86/kernel/irq_32.c | 4 ++--
    arch/x86/kernel/vmlinux.lds.S | 2 +-
    include/linux/percpu-defs.h | 12 ++++++++++++
    3 files changed, 15 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
    index 3b5609f..50fbbe6 100644
    --- a/arch/x86/kernel/irq_32.c
    +++ b/arch/x86/kernel/irq_32.c
    @@ -60,8 +60,8 @@ union irq_ctx {
    static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx);
    static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);

    -static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, hardirq_stack);
    -static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, softirq_stack);
    +static DEFINE_PER_CPU_MULTIPAGE_ALIGNED(union irq_ctx, hardirq_stack, THREAD_SIZE);
    +static DEFINE_PER_CPU_MULTIPAGE_ALIGNED(union irq_ctx, softirq_stack, THREAD_SIZE);

    static void call_on_stack(void *func, void *stack)
    {
    diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
    index d0bb522..bb89947 100644
    --- a/arch/x86/kernel/vmlinux.lds.S
    +++ b/arch/x86/kernel/vmlinux.lds.S
    @@ -273,7 +273,7 @@ SECTIONS
    }

    #if !defined(CONFIG_X86_64) || !defined(CONFIG_SMP)
    - PERCPU(PAGE_SIZE)
    + PERCPU(THREAD_SIZE)
    #endif

    . = ALIGN(PAGE_SIZE);
    diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
    index ce2dc65..ab20d11 100644
    --- a/include/linux/percpu-defs.h
    +++ b/include/linux/percpu-defs.h
    @@ -139,6 +139,18 @@
    __aligned(PAGE_SIZE)

    /*
    + * Declaration/definition used for large per-CPU variables that must be
    + * aligned to something larger than the pagesize.
    + */
    +#define DECLARE_PER_CPU_MULTIPAGE_ALIGNED(type, name, size) \
    + DECLARE_PER_CPU_SECTION(type, name, "..page_aligned") \
    + __aligned(size)
    +
    +#define DEFINE_PER_CPU_MULTIPAGE_ALIGNED(type, name, size) \
    + DEFINE_PER_CPU_SECTION(type, name, "..page_aligned") \
    + __aligned(size)
    +
    +/*
    * Intermodule exports for per-CPU variables. sparse forgets about
    * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to
    * noop if __CHECKER__.

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