[dpdk-dev] [RFC] igb_uio: change ISR to be threaded when using with RT kernel

[Yongxin Liu]

When igb_uio driver is used with RT kernel, the interrupt handler
should not use IRQF_NO_THREAD as a flag, since uio_event_notify will
call rt_spin_lock which might sleep.

Here is the calltrace.

[ 2034.457805] Call Trace:
[ 2034.460818]  <IRQ>
[ 2034.463397]  dump_stack+0x70/0x9a
[ 2034.467281]  ___might_sleep.cold+0xe1/0xf2
[ 2034.471943]  rt_spin_lock+0x55/0x70
[ 2034.475994]  ? __wake_up_common_lock+0x61/0xb0
[ 2034.481004]  __wake_up_common_lock+0x61/0xb0
[ 2034.485842]  __wake_up+0x13/0x20
[ 2034.489635]  uio_event_notify+0x2c/0x50 [uio]
[ 2034.494560]  igbuio_pci_irqhandler+0x1f/0x40 [igb_uio]
[ 2034.500262]  __handle_irq_event_percpu+0x5f/0x3f0
[ 2034.505532]  ? cpuidle_enter_state+0xd3/0x500
[ 2034.510454]  handle_irq_event_percpu+0x4b/0x90
[ 2034.515462]  handle_irq_event+0x3c/0x5b
[ 2034.519864]  handle_edge_irq+0xbb/0x210
[ 2034.524264]  handle_irq+0x23/0x30
[ 2034.528143]  do_IRQ+0x7e/0x150
[ 2034.531764]  common_interrupt+0xf/0xf
[ 2034.535990]  </IRQ>

Signed-off-by: Yongxin Liu <yongxin....@windriver.com>
---
 kernel/linux/igb_uio/igb_uio.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
index 039f5a5f6..9d7380fb7 100644
--- a/kernel/linux/igb_uio/igb_uio.c
+++ b/kernel/linux/igb_uio/igb_uio.c
@@ -221,7 +221,6 @@ igbuio_pci_enable_interrupts(struct rte_uio_pci_dev *udev)
                msix_entry.entry = 0;
                if (pci_enable_msix(udev->pdev, &msix_entry, 1) == 0) {
                        dev_dbg(&udev->pdev->dev, "using MSI-X");
-                       udev->info.irq_flags = IRQF_NO_THREAD;
                        udev->info.irq = msix_entry.vector;
                        udev->mode = RTE_INTR_MODE_MSIX;
                        break;
@@ -229,7 +228,6 @@ igbuio_pci_enable_interrupts(struct rte_uio_pci_dev *udev)
 #else
                if (pci_alloc_irq_vectors(udev->pdev, 1, 1, PCI_IRQ_MSIX) == 1) 
{
                        dev_dbg(&udev->pdev->dev, "using MSI-X");
-                       udev->info.irq_flags = IRQF_NO_THREAD;
                        udev->info.irq = pci_irq_vector(udev->pdev, 0);
                        udev->mode = RTE_INTR_MODE_MSIX;
                        break;
@@ -241,7 +239,6 @@ igbuio_pci_enable_interrupts(struct rte_uio_pci_dev *udev)
 #ifndef HAVE_ALLOC_IRQ_VECTORS
                if (pci_enable_msi(udev->pdev) == 0) {
                        dev_dbg(&udev->pdev->dev, "using MSI");
-                       udev->info.irq_flags = IRQF_NO_THREAD;
                        udev->info.irq = udev->pdev->irq;
                        udev->mode = RTE_INTR_MODE_MSI;
                        break;
@@ -249,7 +246,6 @@ igbuio_pci_enable_interrupts(struct rte_uio_pci_dev *udev)
 #else
                if (pci_alloc_irq_vectors(udev->pdev, 1, 1, PCI_IRQ_MSI) == 1) {
                        dev_dbg(&udev->pdev->dev, "using MSI");
-                       udev->info.irq_flags = IRQF_NO_THREAD;
                        udev->info.irq = pci_irq_vector(udev->pdev, 0);
                        udev->mode = RTE_INTR_MODE_MSI;
                        break;
@@ -259,7 +255,7 @@ igbuio_pci_enable_interrupts(struct rte_uio_pci_dev *udev)
        case RTE_INTR_MODE_LEGACY:
                if (pci_intx_mask_supported(udev->pdev)) {
                        dev_dbg(&udev->pdev->dev, "using INTX");
-                       udev->info.irq_flags = IRQF_SHARED | IRQF_NO_THREAD;
+                       udev->info.irq_flags = IRQF_SHARED;
                        udev->info.irq = udev->pdev->irq;
                        udev->mode = RTE_INTR_MODE_LEGACY;
                        break;
-- 
2.14.4