[PATCHv2 6/8] arm_pmu: explicitly enable/disable SPIs at hotplug

[Geert Uytterhoeven]

Hi Will,

On Mon, Feb 26, 2018 at 4:22 PM, Will Deacon <will.deacon at arm.com> wrote:
> On Mon, Feb 26, 2018 at 04:16:19PM +0100, Geert Uytterhoeven wrote:
>> On Mon, Feb 5, 2018 at 5:42 PM, Mark Rutland <mark.rutland at arm.com> wrote:
>> > To support ACPI systems, we need to request IRQs before CPUs are
>> > hotplugged, and thus we need to request IRQs before we know their
>> > associated PMU.
>> >
>> > This is problematic if a PMU IRQ is pending out of reset, as it may be
>> > taken before we know the PMU, and thus the IRQ handler won't be able to
>> > handle it, leaving it screaming.
>> >
>> > To avoid such problems, lets request all IRQs in a disabled state, and
>> > explicitly enable/disable them at hotplug time, when we're sure the PMU
>> > has been probed.
>> >
>> > Signed-off-by: Mark Rutland <mark.rutland at arm.com>
>>
>> This is now commit 6de3f79112cc26bf in v4.16-rc3, and causes a BUG during
>> CPU offlining (e.g. during system suspend, or during boot with
>> CONFIG_ARM_PSCI_CHECKER=y).
>>
>> With CONFIG_ARM_PSCI_CHECKER=y:
>>
>> psci_checker: PSCI checker started using 6 CPUs
>> psci_checker: Starting hotplug tests
>> psci_checker: Trying to turn off and on again all CPUs
>> BUG: sleeping function called from invalid context at kernel/irq/manage.c:112
>> in_atomic(): 1, irqs_disabled(): 128, pid: 15, name: migration/1
>> no locks held by migration/1/15.
>> irq event stamp: 192
>> hardirqs last  enabled at (191): [<00000000803c2507>]
>> _raw_spin_unlock_irq+0x2c/0x4c
>> hardirqs last disabled at (192): [<000000007f57ad28>] multi_cpu_stop+0x9c/0x140
>> softirqs last  enabled at (0): [<0000000004ee1b58>]
>> copy_process.isra.77.part.78+0x43c/0x1504
>> softirqs last disabled at (0): [<          (null)>]           (null)
>> CPU: 1 PID: 15 Comm: migration/1 Not tainted 4.16.0-rc3-salvator-x #1651
>> Hardware name: Renesas Salvator-X board based on r8a7796 (DT)
>> Call trace:
>>  dump_backtrace+0x0/0x140
>>  show_stack+0x14/0x1c
>>  dump_stack+0xb4/0xf0
>>  ___might_sleep+0x1fc/0x218
>>  __might_sleep+0x70/0x80
>>  synchronize_irq+0x40/0xa8
>>  disable_irq+0x20/0x2c
>
> Given that these things are CPU-affine, I reckon this should be
> disable_irq_nosync. Mark?
>
> Will
>
> --->8
>
> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index 0c2ed11c0603..f63db346c219 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -638,7 +638,7 @@ static int arm_perf_teardown_cpu(unsigned int cpu, struct hlist_node *node)
>                 if (irq_is_percpu_devid(irq))
>                         disable_percpu_irq(irq);
>                 else
> -                       disable_irq(irq);
> +                       disable_irq_nosync(irq);
>         }
>
>         per_cpu(cpu_armpmu, cpu) = NULL;

Tested-by: Geert Uytterhoeven <geert+renesas at glider.be>

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds