linux-kernel - Re: [PATCH v13 0/6] Address error and recovery for AER and DPC

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Date:   Mon, 16 Apr 2018 08:27:53 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     poza@...eaurora.org
Cc:     Sinan Kaya <okaya@...eaurora.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dongdong Liu <liudongdong3@...wei.com>,
        Keith Busch <keith.busch@...el.com>, Wei Zhang <wzhang@...com>,
        Timur Tabi <timur@...eaurora.org>
Subject: Re: [PATCH v13 0/6] Address error and recovery for AER and DPC

On Mon, Apr 16, 2018 at 11:33:13AM +0530, poza@...eaurora.org wrote:
> On 2018-04-16 09:23, Sinan Kaya wrote:
> > On 4/15/2018 11:16 PM, Bjorn Helgaas wrote:
> > > On Mon, Apr 09, 2018 at 10:41:48AM -0400, Oza Pawandeep wrote:
> > > > This patch set brings in error handling support for DPC
> > > > 
> > > > The current implementation of AER and error message broadcasting
> > > > to the
> > > > EP driver is tightly coupled and limited to AER service driver.
> > > > It is important to factor out broadcasting and other link handling
> > > > callbacks. So that not only when AER gets triggered, but also
> > > > when DPC get
> > > > triggered (for e.g. ERR_FATAL), callbacks are handled appropriately.
> > > > 
> > > > DPC should behave identical to AER as far as error handling is
> > > > concerned.
> > > > DPC should remove the devices and not to do recovery for hotplug
> > > > enabled system.
> > > 
> > > Is there a specific bug that's fixed by these patches?  I didn't see
> > > one mentioned in the changelogs.
> > > 
> > 
> > There is no actual bug.
> > 
> > We realized that DPC and hotplug is heavily integrated today. We
> > have use cases for systems without hotplug support but still
> > support DPC. That's the problem we are trying to solve with this
> > patchset.

Apparently there's a problem with systems that have DPC but not
hotplug.  It will be extremely helpful if you can articulate what that
problem is and include it in the appropriate changelog.

> Adding to what Sinan said;
> 
> DPC should handle the error handling and recovery similar to AER,
> because finally both are attempting recovery in some or the other
> way, and for that error handling and recovery framework has to be
> loosely coupled.  It achieves uniformity and transparency to the
> error handling agents such as AER, DPC, with respect to recovery and
> error handling.
> 
> So, this patch-set tries to unify lot of things between error agents
> and make them behave in a well defined way. (be it error (FATAL,
> NON_FATAL) handling or recovery).

I totally support this objective.

Bjorn