From: marc.zyngier@arm•com (Marc Zyngier)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] ARM: irq_work: Do not attempt to IPI on non IPI-capable HW
Date: Wed, 17 Aug 2016 08:41:23 +0100 [thread overview]
Message-ID: <57B41523.6030202@arm.com> (raw)
In-Reply-To: <CAL411-pUUdxN_d76FaXYGtEd7Seewnrin=x2mFEbi1Z48zSRvg@mail.gmail.com>
On 17/08/16 04:15, Peter Chen wrote:
> On Tue, Aug 16, 2016 at 11:26 PM, Marc Zyngier <marc.zyngier@arm•com> wrote:
>> Not all of the ARM HW is IPI capable (i.e. most of the non-SMP
>> systems). Unfortunately, some systems do advertise being SMP
>> capable, even if they have a single core and do not define
>> a cross call method.
>
> Could you example it? I find all current set_smp_cross_call is defined
> under CONFIG_SMP.
This doesn't mean that the system will be SMP at runtime (SMP_ON_UP).
> Or you will change gic code to define set_smp_cross_call at runtime?
No. Also, the GIC is not a universally adopted interrupt controller, as
plenty of system don't have one.
>
>> In this case, irq_work_queue dies
>> as arch_irq_work_has_interrupt() fails to detect this
>> particular case.
>>
>> Let's redefine arch_irq_work_has_interrupt() to actually check
>> if we're IPI capable instead of simply being SMP. This sidesteps
>> the issue entierely.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm•com>
>> ---
>> arch/arm/include/asm/irq_work.h | 6 +++++-
>> arch/arm/include/asm/smp_plat.h | 2 ++
>> arch/arm/kernel/smp.c | 2 +-
>> 3 files changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/irq_work.h b/arch/arm/include/asm/irq_work.h
>> index 712d03e..3ba3583 100644
>> --- a/arch/arm/include/asm/irq_work.h
>> +++ b/arch/arm/include/asm/irq_work.h
>> @@ -5,7 +5,11 @@
>>
>> static inline bool arch_irq_work_has_interrupt(void)
>> {
>> - return is_smp();
>> +#ifdef CONFIG_SMP
>
> Why not using is_smp as condition, it is more strict.
>
> if (is_smp())
> return !!__smp_cross_call;
> else
> return false;
What's the gain? We're trying to check whether we can actually deliver
an IPI. Why should we gate it by finding out whether we're smp_on_up or not?
Thanks,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2016-08-17 7:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-16 15:26 [PATCH] ARM: irq_work: Do not attempt to IPI on non IPI-capable HW Marc Zyngier
2016-08-16 15:52 ` Fabio Estevam
2016-08-16 16:03 ` Marc Zyngier
2016-08-17 3:15 ` Peter Chen
2016-08-17 7:41 ` Marc Zyngier [this message]
2016-08-17 7:58 ` Peter Chen
2016-08-17 8:08 ` Marc Zyngier
2016-08-17 8:28 ` Peter Chen
2016-08-17 9:19 ` Marc Zyngier
2016-08-17 11:27 ` Peter Chen
2016-08-17 12:57 ` Marc Zyngier
2016-08-17 13:28 ` Fabio Estevam
2016-08-30 17:03 ` Marc Zyngier
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