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 09:08:48 +0100 [thread overview]
Message-ID: <57B41B90.3050204@arm.com> (raw)
In-Reply-To: <VI1PR04MB1455E9F56D0EDA0558CC84508B140@VI1PR04MB1455.eurprd04.prod.outlook.com>
On 17/08/16 08:58, Peter Chen wrote:
>
>> 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).
>>
>
> I am puzzled that how you would like to check IPI capable, at runtime
> or according to kernel configuration?
>
>>>>
>>>> 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?
>>
>
> If UP system with CONFIG_SMP enabled, the __smp_cross_call is not
> NULL, but the IPI is not capable. Or am I missing something?
Take an OMAP3 system. It is UP, and doesn't have a GIC, so
__smp_cross_call will be NULL. Yet, it boots with a generic
multi-platform kernel, with SMP on.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2016-08-17 8:08 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
2016-08-17 7:58 ` Peter Chen
2016-08-17 8:08 ` Marc Zyngier [this message]
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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