linux-kernel - Re: [PATCH v2] PCI/LINK: bw_notification: Do not leave interrupt handler NULL

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Date:   Fri, 19 Apr 2019 16:25:48 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     Alexandru Gagniuc <mr.nuke.me@...il.com>, austin_bolen@...l.com,
        alex_gagniuc@...lteam.com, keith.busch@...el.com,
        Shyam_Iyer@...l.com, lukas@...ner.de, okaya@...nel.org,
        torvalds@...ux-foundation.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI/LINK: bw_notification: Do not leave interrupt
 handler NULL

On Fri, Apr 19, 2019 at 03:08:27PM -0600, Alex Williamson wrote:
> On Mon, 25 Mar 2019 17:25:02 -0500, Bjorn Helgaas <helgaas@...nel.org> wrote:
> > On Fri, Mar 22, 2019 at 07:36:51PM -0500, Alexandru Gagniuc wrote:
> > > A threaded IRQ with a NULL handler does not work with level-triggered
> > > interrupts. request_threaded_irq() will return an error:
> > > 
> > >   genirq: Threaded irq requested with handler=NULL and !ONESHOT for irq 16
> > >   pcie_bw_notification: probe of 0000:00:1b.0:pcie010 failed with error -22
> > > 
> > > For level interrupts we need to silence the interrupt before exiting
> > > the IRQ handler, so just clear the PCI_EXP_LNKSTA_LBMS bit there.
> > > 
> > > Fixes: e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth notification")
> > > Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > > Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...il.com>  
> > 
> > Applied with the following subject line to for-linus for v5.1, thanks!
> > 
> >   PCI/LINK: Supply IRQ handler so level-triggered IRQs are acked
> 
> That made it a little tricky to track down this thread.

Yeah, sorry about that.  I've been wondering if I should add
lore.kernel.org URLs when I apply patches.  Maybe this is one good
reason to do that.

Bjorn