Re: [PATCH v2] PCI: dra7xx: mark dra7xx_pcie_msi irq as IRQF_NO_THREAD

[Grygorii Strashko]

On 12/09/2015 05:24 PM, Bjorn Helgaas wrote:
> On Tue, Dec 08, 2015 at 10:05:56AM +0100, Sebastian Andrzej Siewior wrote:
> > * Bjorn Helgaas | 2015-12-04 12:46:19 [-0600]:
> >
> > > The backtrace might be OK (maybe slightly overkill), but all the
> > > stack addresses are certainly irrelevant and distracting.  We only
> > > need enough to recognize the problem.  I don't think the modules list
> > > is relevant either.
> >
> > I would shorten it to the bare minimum. Also the patch description
> > itself could be truncated to the required bitsâ
> >
> > > > diff --git a/drivers/pci/host/pci-dra7xx.c b/drivers/pci/host/pci-dra7xx.c
> > > > index 8c36880..0415192 100644
> > > > --- a/drivers/pci/host/pci-dra7xx.c
> > > > +++ b/drivers/pci/host/pci-dra7xx.c
> > > > @@ -301,8 +301,19 @@ static int __init dra7xx_add_pcie_port(struct dra7xx_pcie *dra7xx,
> > > >   		return -EINVAL;
> > > >   	}
> > > >
> > > > +	/*
> > > > +	 * Mark dra7xx_pcie_msi IRQ as IRQF_NO_THREAD
> > > > +	 * On -RT and if kernel is booting with "threadirqs" cmd line parameter
> > > > +	 * the dra7xx_pcie_msi_irq_handler() will be forced threaded but,
> > > > +	 * in the same time, it's IRQ dispatcher and calls generic_handle_irq(),
> > > > +	 * which, in turn, will be resolved to handle_simple_irq() call.
> > > > +	 * The handle_simple_irq() expected to be called with IRQ disabled, as
> > > > +	 * result kernle will display warning:
> > > > +	 * "irq XXX handler YYY+0x0/0x14 enabled interrupts".
> > > > +	 */
> >
> > ânot to mention this piece. d7ce4377494a ("powerpc/fsl_msi: mark the msi
> > cascade handler IRQF_NO_THREAD") fixes the same bug in arch/ppc so they
> > bypassed you fixing it.
> >
> > > >   	ret = devm_request_irq(&pdev->dev, pp->irq,
> > > > -			       dra7xx_pcie_msi_irq_handler, IRQF_SHARED,
> > > > +			       dra7xx_pcie_msi_irq_handler,
> > > > +			       IRQF_SHARED | IRQF_NO_THREAD,
> > > >   			       "dra7-pcie-msi",	pp);
> > >
> > > There's similar code in exynos_add_pcie_port(), imx6_add_pcie_port(),
> > > and spear13xx_add_pcie_port().  Do they need similar changes?  If not,
> > > why not?
> >
> > You are right. The request for the handler exynos_pcie_msi_irq_handler(),
> > imx6_pcie_msi_handler() and spear13xx_pcie_irq_handler() needs same
> > treatment.
> > Additionally we have:
> >
> > arch/mips/pci/msi-octeon.c: if (request_irq(OCTEON_IRQ_PCI_MSI0, octeon_msi_interrupt0,
> > arch/sparc/kernel/pci_msi.c:    err = request_irq(irq, sparc64_msiq_interrupt, 0,
> > drivers/pci/host/pci-tegra.c:   err = request_irq(msi->irq, tegra_pcie_msi_irq, 0,
> > drivers/pci/host/pcie-rcar.c:   err = devm_request_irq(&pdev->dev, msi->irq1, rcar_pcie_msi_irq,
> > drivers/pci/host/pcie-rcar.c:   err = devm_request_irq(&pdev->dev, msi->irq2, rcar_pcie_msi_irq,
> > drivers/pci/host/pcie-xilinx.c: err = devm_request_irq(dev, port->irq, xilinx_pcie_intr_handler,
> >
> > which require the same kind of fixâ
> >
> > > I see your discussion about DRA7 hardware design, but my impression is
> > > that this problem affects anybody who calls dw_handle_msi_irq() from a
> > > handler registered with IRQF_SHARED.
> >
> > â brecause all of them invoke generic_handle_irq() from the requsted
> > handler. generic_handle_irq grabs raw_locks and this needs to run in
> > raw-irq context.
> > IRQF_SHARED could probably go away. The IRQ is mostlikely exclusive
> > assigned in each SoC for MSI interrupt demux.
>
> It sounds like we should fix all these places at once.  If you
> (Grygorii) work up a patch that does them all, with a more generic
> changelog, then we can solicit testing and acks.

Sure, will do:
- change will be applied for files listed in this thread only
- IRQF_SHARED will be left unchanged
- commit message will be made more generic
- i prefer to keep comment in code for dra7 as is.
Is it ok?


--
regards,
-grygorii
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