On Fri, 17 Nov 2006 14:31:28 +0100
Ingo Molnar <mingo@xxxxxxx> wrote:
>
> * Ingo Molnar <mingo@xxxxxxx> wrote:
>
> > The scheduler on Andreas Friedrich's hyperthreading system stopped
> > working properly as of 2.6.18: the scheduler would never move tasks to
> > another CPU!
>
> correction: the last known working kernel was 2.6.8. The bug predates
> our GIT history so it's older than 1.5 years.
>
How come nobody noticed? Maybe it improved things ;)
I spose it's 2.6.19 material, although it's a bit of a leap into the
unknown.
How many systems will this affect?
CPU#1: set_cpus_allowed(), swapper:1, 3 -> 2
[<c0103bbe>] show_trace_log_lvl+0x34/0x4a
[<c0103ceb>] show_trace+0x2c/0x2e
[<c01045f8>] dump_stack+0x2b/0x2d
[<c0116a77>] set_cpus_allowed+0x52/0xec
[<c0101d86>] cpu_idle_wait+0x2e/0x100
[<c0259c57>] acpi_processor_power_exit+0x45/0x58
[<c0259752>] acpi_processor_remove+0x46/0xea
[<c025c6fb>] acpi_start_single_object+0x47/0x54
[<c025cee5>] acpi_bus_register_driver+0xa4/0xd3
[<c04ab2d7>] acpi_processor_init+0x57/0x77
[<c01004d7>] init+0x146/0x2fd
[<c0103a87>] kernel_thread_helper+0x7/0x10
It seems strange that the kernel is calling acpi_processor_power_exit() at
this stage. It'll have happened because acpi_start_single_object()'s call
to acpi_processor_start() returned non-zero. Why did that happen?
> static int __cpuinit acpi_processor_start(struct acpi_device *device)
> {
> int result = 0;
> acpi_status status = AE_OK;
> struct acpi_processor *pr;
>
>
> pr = acpi_driver_data(device);
>
> result = acpi_processor_get_info(pr);
> if (result) {
> /* Processor is physically not present */
> return 0;
Surely that should be either AE_OK (but why?) or -ESOMETHING.
> }
>
> BUG_ON((pr->id >= NR_CPUS) || (pr->id < 0));
>
> /*
> * Buggy BIOS check
> * ACPI id of processors can be reported wrongly by the BIOS.
> * Don't trust it blindly
> */
> if (processor_device_array[pr->id] != NULL &&
> processor_device_array[pr->id] != device) {
> printk(KERN_WARNING "BIOS reported wrong ACPI id"
> "for the processor\n");
> return -ENODEV;
Andreas wasn't seeing that, right?
> }
> processor_device_array[pr->id] = device;
>
> processors[pr->id] = pr;
>
> result = acpi_processor_add_fs(device);
> if (result)
> goto end;
I'd assume that this is failing. I wonder why?
> status = acpi_install_notify_handler(pr->handle, ACPI_DEVICE_NOTIFY,
> acpi_processor_notify, pr);
whoops, this return value gets lost.
> /* _PDC call should be done before doing anything else (if reqd.). */
> arch_acpi_processor_init_pdc(pr);
> acpi_processor_set_pdc(pr);
>
> acpi_processor_power_init(pr, device);
>
> if (pr->flags.throttling) {
> printk(KERN_INFO PREFIX "%s [%s] (supports",
> acpi_device_name(device), acpi_device_bid(device));
> printk(" %d throttling states", pr->throttling.state_count);
> printk(")\n");
> }
>
> end:
>
> return result;
> }
>
>
>
>
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