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    Subject[PATCH RFC] acpi: Fix unprotected smp_processor_id() in acpi_processor_cst_has_changed()
    The acpi_processor_cst_has_changed() function is invoked from a
    CPU_ONLINE or CPU_DEAD function, which might well execute on CPU 0
    even though the CPU being hotplugged is some other CPU. In addition,
    acpi_processor_cst_has_changed() invokes smp_processor_id() without
    protection, resulting in splats when onlining CPUs.

    This commit therefore changes the smp_processor_id() to pr->id, as is
    used elsewhere in the code, for example, in acpi_processor_add().

    This works for me, but I don't claim to understand ACPI.

    Signed-off-by: Paul E. McKenney <>

    diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
    index 0e8e2de..9e57b06 100644
    --- a/drivers/acpi/processor_idle.c
    +++ b/drivers/acpi/processor_idle.c
    @@ -1159,8 +1159,7 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr)
    * to make the code that updates C-States be called once.

    - if (smp_processor_id() == 0 &&
    - cpuidle_get_driver() == &acpi_idle_driver) {
    + if (pr->id == 0 && cpuidle_get_driver() == &acpi_idle_driver) {

    /* Protect against cpu-hotplug */

     \ /
      Last update: 2012-02-23 22:01    [W:0.020 / U:1.868 seconds]
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