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    SubjectRe: [git pull] sparseirq / irq updates for v2.6.29
    Ingo Molnar wrote:
    > * Ingo Molnar <mingo@elte.hu> wrote:
    >
    >> b2e2fe9: sparseirq: work around __weak alias bug
    >
    > here's that fix, standalone too. Kamalesh, i think this should finally fix
    > the crash you are seeing.
    >
    > Ingo
    >
    > ---------------->
    >>From b2e2fe99628c4f944c3075258e536197b5a4f3f8 Mon Sep 17 00:00:00 2001
    > From: Ingo Molnar <mingo@elte.hu>
    > Date: Mon, 29 Dec 2008 00:16:45 +0100
    > Subject: [PATCH] sparseirq: work around __weak alias bug
    >
    > Impact: fix boot crash if the kernel is built with certain GCC versions
    >
    > GCC has a bug with __weak alias functions: if the functions are in
    > the same compilation unit as their call site, GCC can decide to
    > inline them - and thus rob the linker of the opportunity to override
    > the weak alias with the real thing.
    >
    > This can lead to the boot crash reported by Kamalesh Babulal:
    >
    > ACPI: Core revision 20080926
    > Setting APIC routing to flat
    > BUG: unable to handle kernel NULL pointer dereference at
    > 0000000000000000
    > IP: [<ffffffff8021f9a8>] add_pin_to_irq_cpu+0x14/0x74
    > PGD 0
    > Oops: 0000 [#1] SMP
    > [...]
    >
    > So move the arch_init_chip_data() function from handle.c to manage.c.

    that is not enough.

    need


    [PATCH] sparseirq: mvoe two weak functions to chip.c

    Impact: fix panic

    some gcc compiler will remove the weak global blank function
    Linus noted that we could move those function to other unit to workaround it.

    try to workaround it:
    1. one time path: add printk
    2. multi time path: move to chip.c

    Signed-off-by: Yinghai Lu <yinghai@kernel.org>

    ---
    init/main.c | 9 +++------
    kernel/irq/chip.c | 10 ++++++++++
    kernel/irq/handle.c | 5 -----
    3 files changed, 13 insertions(+), 11 deletions(-)
    Index: linux-2.6/init/main.c
    ===================================================================
    --- linux-2.6.orig/init/main.c
    +++ linux-2.6/init/main.c
    @@ -542,14 +542,11 @@ void __init __weak thread_info_cache_ini
    {
    }

    -int __init __weak arch_early_irq_init(void)
    -{
    - return 0;
    -}
    -
    int __init __weak early_irq_init(void)
    {
    - return arch_early_irq_init();
    + printk(KERN_DEBUG "calling __weak early_irq_init()\n");
    +
    + return 0;
    }

    asmlinkage void __init start_kernel(void)
    Index: linux-2.6/kernel/irq/chip.c
    ===================================================================
    --- linux-2.6.orig/kernel/irq/chip.c
    +++ linux-2.6/kernel/irq/chip.c
    @@ -18,6 +18,16 @@

    #include "internals.h"

    +int __init __weak arch_early_irq_init(void)
    +{
    + return 0;
    +}
    +
    +int __weak arch_init_chip_data(struct irq_desc *desc, int cpu)
    +{
    + return 0;
    +}
    +
    /**
    * dynamic_irq_init - initialize a dynamically allocated irq
    * @irq: irq number to initialize
    Index: linux-2.6/kernel/irq/handle.c
    ===================================================================
    --- linux-2.6.orig/kernel/irq/handle.c
    +++ linux-2.6/kernel/irq/handle.c
    @@ -86,11 +86,6 @@ void init_kstat_irqs(struct irq_desc *de
    desc->kstat_irqs = (unsigned int *)ptr;
    }

    -int __weak arch_init_chip_data(struct irq_desc *desc, int cpu)
    -{
    - return 0;
    -}
    -
    static void init_one_irq_desc(int irq, struct irq_desc *desc, int cpu)
    {
    memcpy(desc, &irq_desc_init, sizeof(struct irq_desc));

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