On Fri, 2014-05-02 at 13:32 +0200, Igor Mammedov wrote: > On Wed, 30 Apr 2014 15:25:51 -0600 > Toshi Kani <[email protected]> wrote: > > > On Mon, 2014-04-14 at 17:11 +0200, Igor Mammedov wrote: > > > acpi_processor_add() assumes that present at boot CPUs > > > are always onlined, it is not so if a CPU failed to become > > > onlined. As result acpi_processor_add() will mark such CPU > > > device as onlined in sysfs and following attempts to > > > online/offline it using /sys/device/system/cpu/cpuX/online > > > attribute will fail. > > > > > > Do not poke into device internals in acpi_processor_add() > > > and touch "struct device { .offline }" attribute, since > > > for CPUs onlined at boot it's set by: > > > topology_init() -> arch_register_cpu() -> register_cpu() > > > before ACPI device tree is parsed, and for hotplugged > > > CPUs it's set when userspace onlines CPU via sysfs. > > > > > > Signed-off-by: Igor Mammedov <[email protected]> > > > --- > > > v2: > > > - fix regression in v1 leading to NULL pointer dereference > > > on CPU unplug, do not remove "pr->dev = dev;" > > > --- > > > drivers/acpi/acpi_processor.c | 1 - > > > 1 files changed, 0 insertions(+), 1 deletions(-) > > > > > > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c > > > index c29c2c3..42d66f8 100644 > > > --- a/drivers/acpi/acpi_processor.c > > > +++ b/drivers/acpi/acpi_processor.c:q > > > @@ -404,7 +404,6 @@ static int acpi_processor_add(struct acpi_device > > > *device, > > > goto err; > > > > > > pr->dev = dev; > > > - dev->offline = pr->flags.need_hotplug_init; > > > > IIRC, this change was necessary to handle the case when maxcpus=X is > > specified at boot. In this case, excessive CPU's dev->offline needs to > > be set to 1. Can you verify this? > Option 'maxcpus' works just fine without and with this patch since a bit > earlier in acpi_processor_add() it exits in case of extra present CPUs: > > #ifdef CONFIG_SMP > if (pr->id >= setup_max_cpus && pr->id != 0) > return 0; > #endif > > and execution doesn't get to the point the patch touches.
This is a separate topic, but I feel that the above code should not be necessary... > The point is that acpi_processor_add() shouldn't touch > dev->offline at all and allow register_cpu() handle it. Sorry, I had confused with cpu->dev.offline in register_cpu() in my recollection. Yes, I agree that we should let register_cpu() to handle it. Acked-by: Toshi Kani <[email protected]> Thanks, -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
