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Date: Mon, 4 May 2015 17:10:26 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Amir Vadai <amirv@mellanox.com>
cc: Jiang Liu <jiang.liu@linux.intel.com>, Bjorn Helgaas <bhelgaas@google.com>,
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Subject: Re: [RFC v1 07/11] net/mlx4: Cache irq_desc->affinity instead of
 irq_desc
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On Mon, 4 May 2015, Amir Vadai wrote:

> On Mon, May 4, 2015 at 6:15 AM, Jiang Liu <jiang.liu@linux.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.

irq_set_affinity_notifier() has been added for exactly this purpose.

Please get rid of your irq_desc abuse.

Thanks,

	tglx


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