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    Subject[tip:sched/urgent] generic-ipi: Fix kexec boot crash by initializing call_single_queue before enabling interrupts
    Commit-ID:  d8ad7d1123a960cc9f276bd499f9325c6f5e1bd1
    Gitweb: http://git.kernel.org/tip/d8ad7d1123a960cc9f276bd499f9325c6f5e1bd1
    Author: Takao Indoh <indou.takao@jp.fujitsu.com>
    AuthorDate: Tue, 29 Mar 2011 12:35:04 -0400
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Fri, 17 Jun 2011 10:17:12 +0200

    generic-ipi: Fix kexec boot crash by initializing call_single_queue before enabling interrupts

    There is a problem that kdump(2nd kernel) sometimes hangs up due
    to a pending IPI from 1st kernel. Kernel panic occurs because IPI
    comes before call_single_queue is initialized.

    To fix the crash, rename init_call_single_data() to call_function_init()
    and call it in start_kernel() so that call_single_queue can be
    initialized before enabling interrupts.

    The details of the crash are:

    (1) 2nd kernel boots up

    (2) A pending IPI from 1st kernel comes when irqs are first enabled
    in start_kernel().

    (3) Kernel tries to handle the interrupt, but call_single_queue
    is not initialized yet at this point. As a result, in the
    generic_smp_call_function_single_interrupt(), NULL pointer
    dereference occurs when list_replace_init() tries to access
    &q->list.next.

    Therefore this patch changes the name of init_call_single_data()
    to call_function_init() and calls it before local_irq_enable()
    in start_kernel().

    Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
    Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
    Acked-by: Neil Horman <nhorman@tuxdriver.com>
    Acked-by: Vivek Goyal <vgoyal@redhat.com>
    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Milton Miller <miltonm@bga.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: kexec@lists.infradead.org
    Link: http://lkml.kernel.org/r/D6CBEE2F420741indou.takao@jp.fujitsu.com
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    include/linux/smp.h | 5 ++++-
    init/main.c | 1 +
    kernel/smp.c | 5 +----
    3 files changed, 6 insertions(+), 5 deletions(-)

    diff --git a/include/linux/smp.h b/include/linux/smp.h
    index 7ad824d..8cc38d3 100644
    --- a/include/linux/smp.h
    +++ b/include/linux/smp.h
    @@ -85,12 +85,15 @@ int smp_call_function_any(const struct cpumask *mask,
    * Generic and arch helpers
    */
    #ifdef CONFIG_USE_GENERIC_SMP_HELPERS
    +void __init call_function_init(void);
    void generic_smp_call_function_single_interrupt(void);
    void generic_smp_call_function_interrupt(void);
    void ipi_call_lock(void);
    void ipi_call_unlock(void);
    void ipi_call_lock_irq(void);
    void ipi_call_unlock_irq(void);
    +#else
    +static inline void call_function_init(void) { }
    #endif

    /*
    @@ -134,7 +137,7 @@ static inline void smp_send_reschedule(int cpu) { }
    #define smp_prepare_boot_cpu() do {} while (0)
    #define smp_call_function_many(mask, func, info, wait) \
    (up_smp_call_function(func, info))
    -static inline void init_call_single_data(void) { }
    +static inline void call_function_init(void) { }

    static inline int
    smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
    diff --git a/init/main.c b/init/main.c
    index cafba67..d7211fa 100644
    --- a/init/main.c
    +++ b/init/main.c
    @@ -542,6 +542,7 @@ asmlinkage void __init start_kernel(void)
    timekeeping_init();
    time_init();
    profile_init();
    + call_function_init();
    if (!irqs_disabled())
    printk(KERN_CRIT "start_kernel(): bug: interrupts were "
    "enabled early\n");
    diff --git a/kernel/smp.c b/kernel/smp.c
    index 73a1951..fb67dfa 100644
    --- a/kernel/smp.c
    +++ b/kernel/smp.c
    @@ -74,7 +74,7 @@ static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
    .notifier_call = hotplug_cfd,
    };

    -static int __cpuinit init_call_single_data(void)
    +void __init call_function_init(void)
    {
    void *cpu = (void *)(long)smp_processor_id();
    int i;
    @@ -88,10 +88,7 @@ static int __cpuinit init_call_single_data(void)

    hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
    register_cpu_notifier(&hotplug_cfd_notifier);
    -
    - return 0;
    }
    -early_initcall(init_call_single_data);

    /*
    * csd_lock/csd_unlock used to serialize access to per-cpu csd resources

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