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    Subject[PATCH] ppc64: Fix CPU hot unplug deadlock
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    Date
    Hi !

    My RTAS locking fixes incorrectly added a spinlock around the function
    used to stop a CPU, that function never returns, thus the lock becomes
    stale. The correct fix is to disable interrupts instead (the RTAS params
    beeing per-CPU, this should be safe enough)

    Ben.

    diff -urN linux-2.5/arch/ppc64/kernel/rtas.c ppc64-linux-2.5/arch/ppc64/kernel/rtas.c
    --- linux-2.5/arch/ppc64/kernel/rtas.c 2004-04-17 12:39:03.253986984 +1000
    +++ ppc64-linux-2.5/arch/ppc64/kernel/rtas.c 2004-04-18 15:35:41.871029480 +1000
    @@ -504,9 +504,9 @@
    void rtas_stop_self(void)
    {
    struct rtas_args *rtas_args = &(get_paca()->xRtas);
    - unsigned long s;

    - spin_lock_irqsave(&rtas.lock, s);
    + local_irq_disable(s);
    +
    rtas_args->token = rtas_token("stop-self");
    BUG_ON(rtas_args->token == RTAS_UNKNOWN_SERVICE);
    rtas_args->nargs = 0;
    @@ -516,7 +516,6 @@
    printk("%u %u Ready to die...\n",
    smp_processor_id(), hard_smp_processor_id());
    enter_rtas((void *)__pa(rtas_args));
    - spin_unlock_irqrestore(&rtas.lock, s);

    panic("Alas, I survived.\n");
    }

    -
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