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Date: Tue, 5 May 2015 12:17:28 +0300
From: Amir Vadai <amirv@...lanox.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Amir Vadai <amirv@...lanox.com>,
Jiang Liu <jiang.liu@...ux.intel.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Randy Dunlap <rdunlap@...radead.org>,
Yinghai Lu <yinghai@...nel.org>,
Borislav Petkov <bp@...en8.de>, Ido Shamay <idos@...lanox.com>,
"David S. Miller" <davem@...emloft.net>,
Or Gerlitz <ogerlitz@...lanox.com>,
Eric Dumazet <edumazet@...gle.com>,
Hadar Hen Zion <hadarh@...lanox.com>,
Eran Ben Elisha <eranbe@...lanox.com>,
Joe Perches <joe@...ches.com>,
Saeed Mahameed <saeedm@...lanox.com>,
Matan Barak <matanb@...lanox.com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Tony Luck <tony.luck@...el.com>, x86@...nel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
netdev <netdev@...r.kernel.org>
Subject: Re: [RFC v1 07/11] net/mlx4: Cache irq_desc->affinity instead of irq_desc
On Mon, May 4, 2015 at 6:10 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Mon, 4 May 2015, Amir Vadai wrote:
>
>> On Mon, May 4, 2015 at 6:15 AM, Jiang Liu <jiang.liu@...ux.intel.com> wrote:
>> > The field 'affinity' in irq_desc won't change once the irq_desc data
>> > structure is created. So cache irq_desc->affinity instead of irq_desc.
>> > This also helps to hide struct irq_desc from device drivers.
>>
>> Hi Jiang,
>>
>> I might not understand the new changes irq core, but up until now
>> affinity was changed when the user changed it through
>> /proc/irq/<IRQ>/smp_affinity.
>> This code is monitoring the affinity from the napi_poll context to
>> detect affinity changes, and prevent napi from keep running on the
>> wrong CPU.
>> Therefore, the affinity can't be cached at the beginning. Please
>> revert this caching.
>
> Sigh. All of this is completely wrong. Polling in the internals of
> irq_desc is just crap.
Hi,
>
> irq_set_affinity_notifier() has been added for exactly this purpose.
rmap is already registered on irq_set_affinity_notifier().
Actually, I did post an extension to the affinity notifier, to use
affinity chain which you rejected [1] (and BTW, convinced me that this
is not the way to do it).
Current code is according to your suggestion.
[1] - https://lkml.org/lkml/2014/5/26/222
Amir
>
> Please get rid of your irq_desc abuse.
>
> Thanks,
>
> tglx
>
>
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