[PATCH v3] PCI: hosts: mark pcie/pci (msi) irq cascade handler as IRQF_NO_THREAD

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On -RT and if kernel is booting with "threadirqs" cmd line parameter
pcie/pci (msi) irq cascade handlers (like dra7xx_pcie_msi_irq_handler())
will be forced threaded and, as result, will generate warnings like:

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
Backtrace:
 (warn_slowpath_common) from [<c0043758>] (warn_slowpath_fmt+0x38/0x40)
 (warn_slowpath_fmt) from [<c0085fd0>] (handle_irq_event_percpu+0x14c/0x174)
 (handle_irq_event_percpu) from [<c008607c>] (handle_irq_event+0x84/0xb8)
 (handle_irq_event) from [<c0089240>] (handle_simple_irq+0x90/0x118)
 (handle_simple_irq) from [<c0085514>] (generic_handle_irq+0x30/0x44)
 (generic_handle_irq) from [<c034a7d4>] (dra7xx_pcie_msi_irq_handler+0x7c/0x8c)
 (dra7xx_pcie_msi_irq_handler) from [<c0086f08>] (irq_forced_thread_fn+0x28/0x5c)
 (irq_forced_thread_fn) from [<c00871dc>] (irq_thread+0x128/0x204)

This happens because 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.

This issue was originally reproduced on TI dra7-evem, but, as was
identified during dicussion [1], other PCI(e) hosts can also suffer
from this issue. So let's fix all them at once and mark pcie/pci (msi)
irq cascade handlers IRQF_NO_THREAD explicitly.

[1] https://lkml.org/lkml/2015/11/20/356

Cc: Kishon Vijay Abraham I <kishon@xxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Jingoo Han <jingoohan1@xxxxxxxxx>
Cc: Kukjin Kim <kgene@xxxxxxxxxx>
Cc: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
Cc: Richard Zhu <Richard.Zhu@xxxxxxxxxxxxx>
Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
Cc: Stephen Warren <swarren@xxxxxxxxxxxxx>
Cc: Alexandre Courbot <gnurou@xxxxxxxxx>
Cc: Simon Horman <horms@xxxxxxxxxxxx>
Cc: Pratyush Anand <pratyush.anand@xxxxxxxxx>
Cc: Michal Simek <michal.simek@xxxxxxxxxx>
Cc: "Sören Brinkmann" <soren.brinkmann@xxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
---
Changes in v3:
 - change applied to all affected pci(e) host drivers in drivers/pci/hosts.
   After some invsetigation I've decided to not touch arch code - it is not easy
   to identify all places which need to be fixed. 
   if it's still required - i can send separate patches for 
   arch/mips/pci/msi-octeon.c and arch/sparc/kernel/pci_msi.c.
Links
v2: https://lkml.org/lkml/2015/11/20/356
v1: https://lkml.org/lkml/2015/11/5/593
ref: https://lkml.org/lkml/2015/11/3/660

 drivers/pci/host/pci-dra7xx.c     | 13 ++++++++++++-
 drivers/pci/host/pci-exynos.c     |  3 ++-
 drivers/pci/host/pci-imx6.c       |  3 ++-
 drivers/pci/host/pci-tegra.c      |  2 +-
 drivers/pci/host/pcie-rcar.c      |  6 ++++--
 drivers/pci/host/pcie-spear13xx.c |  3 ++-
 drivers/pci/host/pcie-xilinx.c    |  3 ++-
 7 files changed, 25 insertions(+), 8 deletions(-)

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);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to request irq\n");
diff --git a/drivers/pci/host/pci-exynos.c b/drivers/pci/host/pci-exynos.c
index 01095e1..d997d22 100644
--- a/drivers/pci/host/pci-exynos.c
+++ b/drivers/pci/host/pci-exynos.c
@@ -522,7 +522,8 @@ static int __init exynos_add_pcie_port(struct pcie_port *pp,
 
 		ret = devm_request_irq(&pdev->dev, pp->msi_irq,
 					exynos_pcie_msi_irq_handler,
-					IRQF_SHARED, "exynos-pcie", pp);
+					IRQF_SHARED | IRQF_NO_THREAD,
+					"exynos-pcie", pp);
 		if (ret) {
 			dev_err(&pdev->dev, "failed to request msi irq\n");
 			return ret;
diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index 22e8224..9ce7cd1 100644
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -537,7 +537,8 @@ static int __init imx6_add_pcie_port(struct pcie_port *pp,
 
 		ret = devm_request_irq(&pdev->dev, pp->msi_irq,
 				       imx6_pcie_msi_handler,
-				       IRQF_SHARED, "mx6-pcie-msi", pp);
+				       IRQF_SHARED | IRQF_NO_THREAD,
+				       "mx6-pcie-msi", pp);
 		if (ret) {
 			dev_err(&pdev->dev, "failed to request MSI irq\n");
 			return ret;
diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
index 3018ae5..3032311 100644
--- a/drivers/pci/host/pci-tegra.c
+++ b/drivers/pci/host/pci-tegra.c
@@ -1288,7 +1288,7 @@ static int tegra_pcie_enable_msi(struct tegra_pcie *pcie)
 
 	msi->irq = err;
 
-	err = request_irq(msi->irq, tegra_pcie_msi_irq, 0,
+	err = request_irq(msi->irq, tegra_pcie_msi_irq, IRQF_NO_THREAD,
 			  tegra_msi_irq_chip.name, pcie);
 	if (err < 0) {
 		dev_err(&pdev->dev, "failed to request IRQ: %d\n", err);
diff --git a/drivers/pci/host/pcie-rcar.c b/drivers/pci/host/pcie-rcar.c
index f4fa6c5..414c336 100644
--- a/drivers/pci/host/pcie-rcar.c
+++ b/drivers/pci/host/pcie-rcar.c
@@ -720,14 +720,16 @@ static int rcar_pcie_enable_msi(struct rcar_pcie *pcie)
 
 	/* Two irqs are for MSI, but they are also used for non-MSI irqs */
 	err = devm_request_irq(&pdev->dev, msi->irq1, rcar_pcie_msi_irq,
-			       IRQF_SHARED, rcar_msi_irq_chip.name, pcie);
+			       IRQF_SHARED | IRQF_NO_THREAD,
+			       rcar_msi_irq_chip.name, pcie);
 	if (err < 0) {
 		dev_err(&pdev->dev, "failed to request IRQ: %d\n", err);
 		goto err;
 	}
 
 	err = devm_request_irq(&pdev->dev, msi->irq2, rcar_pcie_msi_irq,
-			       IRQF_SHARED, rcar_msi_irq_chip.name, pcie);
+			       IRQF_SHARED | IRQF_NO_THREAD,
+			       rcar_msi_irq_chip.name, pcie);
 	if (err < 0) {
 		dev_err(&pdev->dev, "failed to request IRQ: %d\n", err);
 		goto err;
diff --git a/drivers/pci/host/pcie-spear13xx.c b/drivers/pci/host/pcie-spear13xx.c
index b95b756..a6cd823 100644
--- a/drivers/pci/host/pcie-spear13xx.c
+++ b/drivers/pci/host/pcie-spear13xx.c
@@ -279,7 +279,8 @@ static int spear13xx_add_pcie_port(struct pcie_port *pp,
 		return -ENODEV;
 	}
 	ret = devm_request_irq(dev, pp->irq, spear13xx_pcie_irq_handler,
-			       IRQF_SHARED, "spear1340-pcie", pp);
+			       IRQF_SHARED | IRQF_NO_THREAD,
+			       "spear1340-pcie", pp);
 	if (ret) {
 		dev_err(dev, "failed to request irq %d\n", pp->irq);
 		return ret;
diff --git a/drivers/pci/host/pcie-xilinx.c b/drivers/pci/host/pcie-xilinx.c
index 3c7a0d5..4cfa463 100644
--- a/drivers/pci/host/pcie-xilinx.c
+++ b/drivers/pci/host/pcie-xilinx.c
@@ -781,7 +781,8 @@ static int xilinx_pcie_parse_dt(struct xilinx_pcie_port *port)
 
 	port->irq = irq_of_parse_and_map(node, 0);
 	err = devm_request_irq(dev, port->irq, xilinx_pcie_intr_handler,
-			       IRQF_SHARED, "xilinx-pcie", port);
+			       IRQF_SHARED | IRQF_NO_THREAD,
+			       "xilinx-pcie", port);
 	if (err) {
 		dev_err(dev, "unable to request irq %d\n", port->irq);
 		return err;
-- 
2.6.4

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