linux-kernel - Re: [PATCH v2] PCI: dra7xx: mark dra7xx_pcie_msi irq as IRQF_NO

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Date:	Wed, 9 Dec 2015 09:24:23 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Grygorii Strashko <grygorii.strashko@...com>,
	Kishon Vijay Abraham I <kishon@...com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, tony@...mide.com,
	nsekhar@...com, linux-omap@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2] PCI: dra7xx: mark dra7xx_pcie_msi irq as
 IRQF_NO_THREAD

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 bits…
> 
> >> 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".
> >> +	 */
> 
> …not 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 fix…
> 
> >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.
> 
> … 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.

Bjorn
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