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    SubjectRe: [PATCH 1/3] stop_machine: kill __stop_machine()
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    On Thu, 2011-06-16 at 05:12 -0700, Peter Zijlstra wrote:
    > On Tue, 2011-06-14 at 19:06 +0200, Tejun Heo wrote:
    > Please have a look at:
    >
    > ---
    > commit d91309f69b7bdb64aeb30106fde8d18c5dd354b5
    > Author: Peter Zijlstra <peterz@infradead.org>
    > Date: Fri Feb 11 22:07:46 2011 +0100
    >
    > x86: Fix text_poke_smp_batch() deadlock
    >
    > Fix this deadlock - we are already holding the mutex:
    >
    ...
    > diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
    > index 1236085..7038b95 100644
    > --- a/arch/x86/kernel/alternative.c
    > +++ b/arch/x86/kernel/alternative.c
    > @@ -671,7 +671,7 @@ void __kprobes text_poke_smp_batch(struct text_poke_param *params, int n)
    >
    > atomic_set(&stop_machine_first, 1);
    > wrote_text = 0;
    > - stop_machine(stop_machine_text_poke, (void *)&tpp, NULL);
    > + __stop_machine(stop_machine_text_poke, (void *)&tpp, NULL);
    > }
    >
    > #if defined(CONFIG_DYNAMIC_FTRACE) || defined(HAVE_JUMP_LABEL)
    >

    Peter, So it looks like we are allowing a new cpu to come online in
    parallel, while we poke the text? Isn't it a problem? What am I missing?

    thanks,
    suresh



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