linux-kernel - Re: [PATCH] PCI: let pci_request_irq properly deal with threaded interrupts

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Date:   Tue, 31 Jul 2018 06:13:17 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.org,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Sebastian Reichel <sre@...nel.org>, Milo Kim <milo.kim@...com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH] PCI: let pci_request_irq properly deal with threaded
 interrupts

On Tue, Jul 31, 2018 at 09:01:12AM +0100, Russell King - ARM Linux wrote:
> On Tue, Jul 31, 2018 at 12:50:21AM +0200, Thomas Gleixner wrote:
> > On Mon, 30 Jul 2018, Bjorn Helgaas wrote:
> > 
> > > [+cc maintainers of possibly erroneous callers of request_threaded_irq()]
> > > 
> > > On Mon, Jul 30, 2018 at 04:30:28PM -0500, Bjorn Helgaas wrote:
> > > > [+cc Thomas, Christoph, LKML]
> > > > 
> > > > On Mon, Jul 30, 2018 at 12:03:42AM +0200, Heiner Kallweit wrote:
> > > > > If we have a threaded interrupt with the handler being NULL, then
> > > > > request_threaded_irq() -> __setup_irq() will complain and bail out
> > > > > if the IRQF_ONESHOT flag isn't set. Therefore check for the handler
> > > > > being NULL and set IRQF_ONESHOT in this case.
> > > > > 
> > > > > This change is needed to migrate the mei_me driver to
> > > > > pci_alloc_irq_vectors() and pci_request_irq().
> > > > > 
> > > > > Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> > > > 
> > > > I'd like an ack from Thomas because this requirement about IRQF_ONESHOT
> > > > usage isn't mentioned in the request_threaded_irq() function doc or
> > > > Documentation/
> > > 
> > > Possibly these other request_threaded_irq() callers are similarly
> > > broken?  I can't tell for sure about tda998x_create(), but all the
> > > others certainly call request_threaded_irq() with "handler == NULL"
> > > and irqflags that do not contain IRQF_ONESHOT:
> > > 
> > >   tda998x_create()
> > >     request_threaded_irq(client->irq, NULL, ..., irqd_get_trigger_type(), ...)
> > >     (I can't tell what irqd_get_trigger_type() does)
> > 
> > It reads the trigger type back from the irq chip (level/edge/polarity) but
> > does not return with the ONESHOT bit set.
> 
> What tree are you (Bjorn) using there?  Looking in my git history,
> request_threaded_irq() was added in January 2014, as:
> 
> +               irqf_trigger =
> +                       irqd_get_trigger_type(irq_get_irq_data(client->irq));
> +               ret = request_threaded_irq(client->irq, NULL,
> +                                          tda998x_irq_thread,
> +                                          irqf_trigger | IRQF_ONESHOT,
> +                                          "tda998x", priv);
> 
> and updated more recently for the CEC support in ae81553c30ef
> ("drm/i2c: tda998x: allow interrupt to be shared") to be:
> 
> -               irqf_trigger =
> +               irq_flags =
>                         irqd_get_trigger_type(irq_get_irq_data(client->irq));
> +               irq_flags |= IRQF_SHARED | IRQF_ONESHOT;
>                 ret = request_threaded_irq(client->irq, NULL,
> -                                          tda998x_irq_thread,
> -                                          irqf_trigger | IRQF_ONESHOT,
> +                                          tda998x_irq_thread, irq_flags,
>                                            "tda998x", priv);
> 
> In all cases, IRQF_ONESHOT has been set for this threaded interrupt.
> 
> I've also checked drm-next, and it doesn't show anything like what
> Bjorn quoted.
> 
> Confused.  Bjorn, can you double check that what you think are
> erroneous request_threaded_irq() calls are actually as per what
> you quoted please?

I was looking at v4.18-rc1, but in the case of tda998x_create(), I
overlooked this line:

  irq_flags |= IRQF_SHARED | IRQF_ONESHOT;

Sorry!