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Date: Fri, 4 Dec 2015 23:22:50 +0200 From: Grygorii Strashko <grygorii.strashko@...com> To: Bjorn Helgaas <helgaas@...nel.org> CC: 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>, Sebastian Andrzej Siewior <bigeasy@...utronix.de> Subject: Re: [PATCH v2] PCI: dra7xx: mark dra7xx_pcie_msi irq as IRQF_NO_THREAD On 12/04/2015 08:46 PM, Bjorn Helgaas wrote: > Hi Grygorii, > > On Fri, Nov 20, 2015 at 03:59:26PM +0200, Grygorii Strashko wrote: >> On -RT, TI DRA7 PCIe driver always produces below backtrace when the >> first PCI interrupt is triggered: >> >> ------------[ cut here ]------------ >> WARNING: CPU: 1 PID: 82 at kernel/irq/handle.c:150 handle_irq_event_percpu+0x14c/0x174() >> irq 460 handler irq_default_primary_handler+0x0/0x14 enabled interrupts [...] >> [<c00891b0>] (handle_simple_irq) from [<c0085514>] (generic_handle_irq+0x30/0x44) >> r5:ee4a9020 r4:000001cc >> [<c00854e4>] (generic_handle_irq) from [<c034a7d4>] (dra7xx_pcie_msi_irq_handler+0x7c/0x8c) >> r5:ee4a9020 r4:00000001 >> [<c034a758>] (dra7xx_pcie_msi_irq_handler) from [<c0086f08>] (irq_forced_thread_fn+0x28/0x5c) >> r5:ee1d0900 r4:ee4b59c0 >> [<c0086ee0>] (irq_forced_thread_fn) from [<c00871dc>] (irq_thread+0x128/0x204) >> r7:00000001 r6:00000000 r5:ee4d2000 r4:ee4b59e4 >> [<c00870b4>] (irq_thread) from [<c005e2fc>] (kthread+0xd4/0xec) >> r10:00000000 r9:00000000 r8:00000000 r7:c00870b4 r6:ee4b59c0 r5:ee4b5a00 >> r4:00000000 >> [<c005e228>] (kthread) from [<c000faa8>] (ret_from_fork+0x14/0x2c) >> r7:00000000 r6:00000000 r5:c005e228 r4:ee4b5a00 >> ---[ end trace 0000000000000002 ]--- > > 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'll take this into account. Is this blocker for this patch now? > >> This backtrace is triggered because dra7xx_pcie_msi_irq_handler() >> forced to be threaded by default on -RT but, in the same time, it's >> IRQ dispatcher and calls generic_handle_irq(), which leads to >> handle_simple_irq() call. The handle_simple_irq() expected to be >> called with IRQ disabled. >> >> The same issue will also happen if kernel will boot with "threadirqs" >> cmdline parameter (CONFIG_IRQ_FORCED_THREADING). >> >> As discussed in [1], the current DRA7 PCIe hw configuration supports >> 32 interrupts, which cannot change because it's hardwired in silicon, >> this is a single status read and assuming that only a few (most of the >> time it will be exactly ONE) of those interrupts are pending at the >> same time is pretty much a sane assumption. And recommended fix for >> this issue is to request dra7xx_pcie_msi IRQ with IRQF_NO_THREAD flag. >> >> [1] https://lkml.org/lkml/2015/11/3/660 >> >> Cc: Thomas Gleixner <tglx@...utronix.de> >> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de> >> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com> >> --- >> Changes in v2: >> - comment in code truncated >> Link on v1: >> https://lkml.org/lkml/2015/11/5/593 >> drivers/pci/host/pci-dra7xx.c | 13 ++++++++++++- >> 1 file changed, 12 insertions(+), 1 deletion(-) >> >> 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". >> + */ >> 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? > > 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. Issue fixed by this patch is not related to IRQF_SHARED. It will happen on -RT or if kernel will boot with "threadirqs" cmd line parameter - in both cases these PCI IRQ handlers will be forced to be threaded and, as result, generic_handle_irq() will produce above backtrace. Personally, I don't have strong opinion about "should similar change be applied to other PCI drivers or not?" And I think, that owners of those driver should make such decision. -- regards, -grygorii -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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