When pciehp is converted to threaded IRQ handling, removal of unplugged
devices below a PCIe hotplug port happens synchronously in the IRQ
thread. Removal of devices typically entails a call to free_irq() by
their drivers.
If those devices share their IRQ with the hotplug port, free_irq()
deadlocks because it calls synchronize_irq() to wait for all hard IRQ
handlers as well as all threads sharing the IRQ to finish.
Actually it's sufficient to wait only for the IRQ thread of the removed
device, so call synchronize_hardirq() to wait for all hard IRQ handlers
to finish, but no longer for any threads. Compensate by rearranging the
control flow in irq_wait_for_interrupt() such that the device's thread
is allowed to run one last time after kthread_stop() has been called.
Stack trace for posterity:
INFO: task irq/17-pciehp:94 blocked for more than 120 seconds.
schedule+0x28/0x80
synchronize_irq+0x6e/0xa0
__free_irq+0x15a/0x2b0
free_irq+0x33/0x70
pciehp_release_ctrl+0x98/0xb0
pcie_port_remove_service+0x2f/0x40
device_release_driver_internal+0x157/0x220
bus_remove_device+0xe2/0x150
device_del+0x124/0x340
device_unregister+0x16/0x60
remove_iter+0x1a/0x20
device_for_each_child+0x4b/0x90
pcie_port_device_remove+0x1e/0x30
pci_device_remove+0x36/0xb0
device_release_driver_internal+0x157/0x220
pci_stop_bus_device+0x7d/0xa0
pci_stop_bus_device+0x3d/0xa0
pci_stop_and_remove_bus_device+0xe/0x20
pciehp_unconfigure_device+0xb8/0x160
pciehp_disable_slot+0x84/0x130
pciehp_ist+0x158/0x190
irq_thread_fn+0x1b/0x50
irq_thread+0x143/0x1a0
kthread+0x111/0x130
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
---
kernel/irq/manage.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index daeabd791d58..0531f645bfea 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -790,9 +790,19 @@ static irqreturn_t irq_forced_secondary_handler(int irq, void *dev_id)
static int irq_wait_for_interrupt(struct irqaction *action)
{
- set_current_state(TASK_INTERRUPTIBLE);
+ for (;;) {
+ set_current_state(TASK_INTERRUPTIBLE);
- while (!kthread_should_stop()) {
+ if (kthread_should_stop()) {
+ /* may need to run one last time. */
+ if (test_and_clear_bit(IRQTF_RUNTHREAD,
+ &action->thread_flags)) {
+ __set_current_state(TASK_RUNNING);
+ return 0;
+ }
+ __set_current_state(TASK_RUNNING);
+ return -1;
+ }
if (test_and_clear_bit(IRQTF_RUNTHREAD,
&action->thread_flags)) {
@@ -800,10 +810,7 @@ static int irq_wait_for_interrupt(struct irqaction *action)
return 0;
}
schedule();
- set_current_state(TASK_INTERRUPTIBLE);
}
- __set_current_state(TASK_RUNNING);
- return -1;
}
/*
@@ -1024,7 +1031,7 @@ static int irq_thread(void *data)
/*
* This is the regular exit path. __free_irq() is stopping the
* thread via kthread_stop() after calling
- * synchronize_irq(). So neither IRQTF_RUNTHREAD nor the
+ * synchronize_hardirq(). So neither IRQTF_RUNTHREAD nor the
* oneshot mask bit can be set. We cannot verify that as we
* cannot touch the oneshot mask at this point anymore as
* __setup_irq() might have given out currents thread_mask
@@ -1629,7 +1636,7 @@ static struct irqaction *__free_irq(struct irq_desc *desc, void *dev_id)
unregister_handler_proc(irq, action);
/* Make sure it's not being used on another CPU: */
- synchronize_irq(irq);
+ synchronize_hardirq(irq);
#ifdef CONFIG_DEBUG_SHIRQ
/*
--
2.17.1
