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    SubjectRe: [ACPI] ACPI using smp_processor_id in preemptible code
    Date
    On Monday 10 January 2005 08:04 pm, Li Shaohua wrote:
    > On Mon, 2005-01-10 at 17:55, Pavel Machek wrote:
    > > > >I enabled CPU hotplug and preemptible debugging... now I get...
    > > > >
    > > > >BUG: using smp_processor_id() in preemptible [00000001] code:
    > > > >swapper/0
    > > > >caller is acpi_processor_idle+0xb/0x235
    > > > > [<c020ba28>] smp_processor_id+0xa8/0xc0
    > > > > [<c02338ce>] acpi_processor_idle+0xb/0x235
    > > > > [<c02338c3>] acpi_processor_idle+0x0/0x235
    > > > > [<c02338ce>] acpi_processor_idle+0xb/0x235
    > > > > [<c02338c3>] acpi_processor_idle+0x0/0x235
    > > > > [<c02338c3>] acpi_processor_idle+0x0/0x235
    > > > > [<c02338c3>] acpi_processor_idle+0x0/0x235
    > > > > [<c0101115>] cpu_idle+0x75/0x110
    > > > > [<c04f5988>] start_kernel+0x158/0x180
    > > > > [<c04f5390>] unknown_bootoption+0x0/0x1e0
    > > > It doesn't trouble to me. It's in idle thread.
    > >
    > > You mean it does not happen to you? On my machine it fills logs very
    > > quickly...
    > What I mean is idle thread can't be migrated so this doesn't impact the
    > correctness. I guess the preemptible debugging can't recognise such
    > situation.
    >

    Why don't you just move that statement down, like in the patch below.
    Also, if processor is not registered but idle thread managed to call
    acpi_processor_idle I think it's BUG()...

    I also cut out unnecessary local variable initializations.

    Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

    --
    Dmitry

    ===== drivers/acpi/processor.c 1.72 vs edited =====
    --- 1.72/drivers/acpi/processor.c 2004-12-03 02:25:47 -05:00
    +++ edited/drivers/acpi/processor.c 2005-01-10 20:58:38 -05:00
    @@ -337,15 +337,11 @@
    static void
    acpi_processor_idle (void)
    {
    - struct acpi_processor *pr = NULL;
    - struct acpi_processor_cx *cx = NULL;
    - unsigned int next_state = 0;
    - unsigned int sleep_ticks = 0;
    - u32 t1, t2 = 0;
    -
    - pr = processors[smp_processor_id()];
    - if (!pr)
    - return;
    + struct acpi_processor *pr;
    + struct acpi_processor_cx *cx;
    + unsigned int next_state;
    + unsigned int sleep_ticks;
    + u32 t1, t2;

    /*
    * Interrupts must be disabled during bus mastering calculations and
    @@ -361,6 +357,10 @@
    local_irq_enable();
    return;
    }
    +
    + pr = processors[smp_processor_id()];
    + if (!pr)
    + BUG();

    cx = &(pr->power.states[pr->power.state]);

    -
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