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From: Thomas Gleixner <tglx@linutronix.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Keith Busch <kbusch@kernel.org>,
	Dongli Zhang <dongli.zhang@oracle.com>,
	fin4478 fin4478 <fin4478@hotmail.com>,
	"keith.busch@intel.com" <keith.busch@intel.com>,
	"axboe@fb.com" <axboe@fb.com>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	linux-kernel@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: A kernel warning when entering suspend
Date: Fri, 5 Apr 2019 13:35:41 +0200 (CEST)
Message-ID: <alpine.DEB.2.21.1904051331270.1802@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20190404225014.GB31281@ming.t460p>

On Fri, 5 Apr 2019, Ming Lei wrote:
> On Thu, Apr 04, 2019 at 04:29:56PM -0600, Keith Busch wrote:
> > On Fri, Apr 05, 2019 at 06:19:50AM +0800, Ming Lei wrote:
> > > Also in current blk-mq implementation, one irq may become shutdown
> > > because of CPU hotplug even though when there is in-flight request
> > > on the queue served by the irq. Then we depend on timeout handler to
> > > cover this case, and this irq may be enabled in the timeout handler too,
> > > please see nvme_poll_irqdisable().
> > 
> > Right, but when the last CPU mapped to an hctx is taken offline, we really
> > ought to have blk-mq wait for that hctx to reap all outstanding requests
> > before letting the notifier continue with offlining that CPU. We just
> > don't have the infrastructure to freeze an individual hctx yet.
> 
> Looks this issue isn't unique for storage device, anyone knows how other
> device drivers deal with this situation? For example, one network packet is
> submitted to NIC controller and not got completed, then the interrupt
> may become down because of CPU hotplug.

If the interrupt is managed yes.

That was the constraint of managed interrupts from the very beginning:

  The driver/subsystem has to quiesce the interrupt line and the associated
  queue _before_ it gets shutdown in CPU unplug and not fiddle with it
  until it's restarted by the core when the CPU is plugged in again.

Thanks,

	tglx

      reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <AM6PR06MB50637026B0E7D87341BF47A3A1500@AM6PR06MB5063.eurprd06.prod.outlook.com>
     [not found] ` <20190404085524.GA24927@ming.t460p>
     [not found]   ` <dbc75de4-aefc-b7da-e86a-91da37f463cf@oracle.com>
     [not found]     ` <alpine.DEB.2.21.1904041812350.1802@nanos.tec.linutronix.de>
     [not found]       ` <20190404221948.GB30656@ming.t460p>
     [not found]         ` <20190404222955.GA25081@localhost.localdomain>
2019-04-04 22:50           ` Ming Lei
2019-04-05 11:35             ` Thomas Gleixner [this message]

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