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From: Thomas Gleixner <tglx@linutronix.de>
To: Jacob Keller <jacob.e.keller@intel.com>,
	Nitesh Narayan Lal <nitesh@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	helgaas@kernel.org, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, linux-pci@vger.kernel.org,
	intel-wired-lan@lists.osuosl.org, frederic@kernel.org,
	sassmann@redhat.com, jesse.brandeburg@intel.com,
	lihong.yang@intel.com, jeffrey.t.kirsher@intel.com,
	jlelli@redhat.com, hch@infradead.org, bhelgaas@google.com,
	mike.marciniszyn@intel.com, dennis.dalessandro@intel.com,
	thomas.lendacky@amd.com, jiri@nvidia.com, mingo@redhat.com,
	juri.lelli@redhat.com, vincent.guittot@linaro.org,
	lgoncalv@redhat.com, Jakub Kicinski <kuba@kernel.org>
Subject: Re: [PATCH v4 4/4] PCI: Limit pci_alloc_irq_vectors() to housekeeping CPUs
Date: Tue, 27 Oct 2020 15:28:16 +0100
Message-ID: <87mu07216n.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <586e249a-1078-9fe9-22d4-b3c1ec0a3a5e@intel.com>

On Mon, Oct 26 2020 at 16:08, Jacob Keller wrote:
> On 10/26/2020 3:49 PM, Thomas Gleixner wrote:
>> On Mon, Oct 26 2020 at 18:22, Nitesh Narayan Lal wrote:
>>> I don't think there is currently a way to control the enablement/disablement of
>>> interrupts from the userspace.
>> 
>> You cannot just disable the interrupt. You need to make sure that the
>> associated queue is shutdown or quiesced _before_ the interrupt is shut
>> down.
>
> Could this be handled with a callback to the driver/hw? I know Intel HW
> should support this type of quiesce/shutdown.

We can't have a callback from the interrupt shutdown code as you have to
wait for the queue to drain packets in flight. Something like this

     mark queue as going down (no more tx queueing)
     tell hardware not to route RX packets to it
     consume pending RX
     wait for already queued TX packets to be sent

Look what the block people did. They have a common multi-instance
hotplug state and they register each context (queue) as an instance. The
hotplug core invokes the corresponding callbacks when bringing a CPU up
or when shutting it down.

Thanks,

        tglx



  reply index

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-28 18:35 [PATCH v4 0/4] isolation: limit msix vectors " Nitesh Narayan Lal
2020-09-28 18:35 ` [PATCH v4 1/4] sched/isolation: API to get number of " Nitesh Narayan Lal
2020-09-28 18:35 ` [PATCH v4 2/4] sched/isolation: Extend nohz_full to isolate managed IRQs Nitesh Narayan Lal
2020-10-23 13:25   ` Peter Zijlstra
2020-10-23 13:29     ` Frederic Weisbecker
2020-10-23 13:57       ` Nitesh Narayan Lal
2020-10-23 13:45     ` Nitesh Narayan Lal
2020-09-28 18:35 ` [PATCH v4 3/4] i40e: Limit msix vectors to housekeeping CPUs Nitesh Narayan Lal
2020-09-28 18:35 ` [PATCH v4 4/4] PCI: Limit pci_alloc_irq_vectors() " Nitesh Narayan Lal
2020-09-28 21:59   ` Bjorn Helgaas
2020-09-29 17:46     ` Christoph Hellwig
2020-10-16 12:20   ` Peter Zijlstra
2020-10-18 18:14     ` Nitesh Narayan Lal
2020-10-19 11:11       ` Peter Zijlstra
2020-10-19 14:00         ` Marcelo Tosatti
2020-10-19 14:25           ` Nitesh Narayan Lal
2020-10-20  7:30           ` Peter Zijlstra
2020-10-20 13:00             ` Nitesh Narayan Lal
2020-10-20 13:41               ` Peter Zijlstra
2020-10-20 14:39                 ` Nitesh Narayan Lal
2020-10-22 17:47                   ` Nitesh Narayan Lal
2020-10-23  8:58                     ` Peter Zijlstra
2020-10-23 13:10                       ` Nitesh Narayan Lal
2020-10-23 21:00                         ` Thomas Gleixner
2020-10-26 13:35                           ` Nitesh Narayan Lal
2020-10-26 13:57                             ` Thomas Gleixner
2020-10-26 17:30                           ` Marcelo Tosatti
2020-10-26 19:00                             ` Thomas Gleixner
2020-10-26 19:11                               ` Marcelo Tosatti
2020-10-26 19:21                               ` Jacob Keller
2020-10-26 20:11                                 ` Thomas Gleixner
2020-10-26 21:11                                   ` Jacob Keller
2020-10-26 21:50                                     ` Thomas Gleixner
2020-10-26 22:13                                       ` Jakub Kicinski
2020-10-26 22:46                                         ` Thomas Gleixner
2020-10-26 22:52                                         ` Jacob Keller
2020-10-26 22:22                                       ` Nitesh Narayan Lal
2020-10-26 22:49                                         ` Thomas Gleixner
2020-10-26 23:08                                           ` Jacob Keller
2020-10-27 14:28                                             ` Thomas Gleixner [this message]
2020-10-27 11:47                                         ` Marcelo Tosatti
2020-10-27 14:43                                           ` Thomas Gleixner
2020-10-19 14:21         ` Frederic Weisbecker
2020-10-20 14:16   ` Thomas Gleixner
2020-10-20 16:18     ` Nitesh Narayan Lal
2020-10-20 18:07       ` Thomas Gleixner
2020-10-21 20:25         ` Thomas Gleixner
2020-10-21 21:04           ` Nitesh Narayan Lal
2020-10-22  0:02           ` Jakub Kicinski
2020-10-22  0:27             ` Jacob Keller
2020-10-22  8:28             ` Thomas Gleixner
2020-10-22 12:28           ` Marcelo Tosatti
2020-10-22 22:39             ` Thomas Gleixner
2020-10-01 15:49 ` [PATCH v4 0/4] isolation: limit msix vectors " Frederic Weisbecker
2020-10-08 21:40   ` Nitesh Narayan Lal

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