On 9/8/2025 4:48 PM, Bjorn Helgaas wrote:
On Mon, Sep 08, 2025 at 04:29:32PM -0500, Mario Limonciello (kernel.org) wrote:
On 9/8/2025 4:03 PM, Bjorn Helgaas wrote:
On Mon, Aug 11, 2025 at 11:35:10AM -0500, Mario Limonciello (AMD) wrote:
When a USB4 dock is unplugged the PCIe bridge it's connected to will
issue a "Link Down" and "Card not detected event". The PCI core will
treat this as a surprise hotplug event and unconfigure all downstream
devices. This involves setting the device error state to
`pci_channel_io_perm_failure` which pci_dev_is_disconnected() will check.
There's nothing special about USB4 here, right? I guess the same
happens with any surprise hotplug remove?
Correct.
pciehp_unconfigure_device() does the pci_dev_set_io_state(dev,
pci_channel_io_perm_failure) part on everything that got removed, so
that part is pretty straightforward.
It doesn't make sense to runtime resume disconnected devices to D0 and
report the (expected) error, so bail early.
Can you include a hint about where the runtime resume happens? It
seems unintuitive to power up removed devices.
Here's the whole trace. Basically as part of the base driver release the
device is runtime resumed.
Do you want me to respin and try to incorporate a sentence or two into the
commit text?
Yes, please.
OK, will do.
I guess maybe we are basically here inside the
pm_runtime_get_sync() here?
pciehp_unconfigure_device
pci_stop_and_remove_bus_device
device_release_driver
device_remove
pci_device_remove
pm_runtime_get_sync <--
drv->remove
I guess it's the pm_runtime_get_sync() that eventually lands us in
pci_power_up()?
And I guess we can't really check whether the device is already gone
in pci_device_remove() because we still want to run the driver
.remove() method and other things to clean up.
I suppose everything we call just needs to be aware that its device
may be already gone?
Yes, exactly.
[ 37.237841] dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
[ 37.237858] pci_power_up.cold+0x86/0xc1
[ 37.237867] ? __pfx_pci_power_up (drivers/pci/pci.c:1360)
[ 37.237876] ? prb_commit (kernel/printk/printk_ringbuffer.c:1748)
[ 37.237883] ? __pfx_prb_read_valid
(kernel/printk/printk_ringbuffer.c:2184)
[ 37.237889] pci_pm_power_up_and_verify_state (drivers/pci/pci.c:1146
drivers/pci/pci.c:1201 drivers/pci/pci.c:3206)
[ 37.237897] ? __pfx_pci_pm_power_up_and_verify_state
(drivers/pci/pci.c:3204)
[ 37.237903] ? __pfx_rpm_resume (drivers/base/power/runtime.c:785)
[ 37.237911] pci_pm_runtime_resume (drivers/pci/pci-driver.c:561
drivers/pci/pci-driver.c:1349)
[ 37.237918] __rpm_callback (drivers/base/power/runtime.c:406)
[ 37.237923] ? __pfx__raw_spin_lock (kernel/locking/spinlock.c:153)
[ 37.237932] rpm_callback (drivers/base/power/runtime.c:444)
[ 37.237936] ? __pfx_pci_pm_runtime_resume (drivers/pci/pci-driver.c:1338)
[ 37.237941] rpm_resume (drivers/base/power/runtime.c:943)
[ 37.237946] ? __pfx_rpm_resume (drivers/base/power/runtime.c:785)
[ 37.237951] ? _raw_spin_lock_irqsave (./include/linux/instrumented.h:96
./include/linux/atomic/atomic-instrumented.h:1301
./include/asm-generic/qspinlock.h:111 ./include/linux/spinlock.h:187
./include/linux/spinlock_api_smp.h:111 kernel/locking/spinlock.c:162)
[ 37.237954] ? __pfx__raw_spin_lock_irqsave
(kernel/locking/spinlock.c:161)
[ 37.237958] ? mutex_lock (./include/linux/instrumented.h:96
./include/linux/atomic/atomic-instrumented.h:4457 kernel/locking/mutex.c:157
kernel/locking/mutex.c:273)
[ 37.237965] __pm_runtime_resume (drivers/base/power/runtime.c:1192)
[ 37.237971] device_release_driver_internal (drivers/base/dd.c:1111
(discriminator 1) drivers/base/dd.c:1252 (discriminator 1)
drivers/base/dd.c:1297 (discriminator 1))
[ 37.237978] ? pci_pme_active (drivers/pci/pci.c:2521)
[ 37.237984] pci_stop_bus_device (drivers/pci/remove.c:44
drivers/pci/remove.c:107)
[ 37.237992] pci_stop_bus_device (drivers/pci/remove.c:102 (discriminator
1))
[ 37.237997] pci_stop_and_remove_bus_device (drivers/pci/remove.c:142)
[ 37.238003] pciehp_unconfigure_device
(drivers/pci/hotplug/pciehp_pci.c:124)
[ 37.238011] ? __pfx_pciehp_unconfigure_device
(drivers/pci/hotplug/pciehp_pci.c:96)
[ 37.238017] ? _dev_info (drivers/base/core.c:4983)
[ 37.238025] pciehp_disable_slot (drivers/pci/hotplug/pciehp_ctrl.c:115
drivers/pci/hotplug/pciehp_ctrl.c:355 drivers/pci/hotplug/pciehp_ctrl.c:364)
[ 37.238030] ? __pfx_pciehp_disable_slot
(drivers/pci/hotplug/pciehp_ctrl.c:360)
[ 37.238035] ? __pfx_mutex_unlock (kernel/locking/mutex.c:531)
[ 37.238039] ? mutex_lock_interruptible (kernel/locking/mutex.c:992)
[ 37.238047] pciehp_handle_presence_or_link_change
(drivers/pci/hotplug/pciehp_ctrl.c:253)
[ 37.238054] ? down_read (kernel/locking/rwsem.c:174
kernel/locking/rwsem.c:182 kernel/locking/rwsem.c:257
kernel/locking/rwsem.c:249 kernel/locking/rwsem.c:1260
kernel/locking/rwsem.c:1274 kernel/locking/rwsem.c:1539)
[ 37.238061] ? __pfx_pciehp_handle_presence_or_link_change
(drivers/pci/hotplug/pciehp_ctrl.c:232)
[ 37.238068] ? __pfx_down_read (kernel/locking/rwsem.c:1535)
[ 37.238074] ? __pfx_pciehp_ist (drivers/pci/hotplug/pciehp_hpc.c:728)
[ 37.238079] pciehp_ist (drivers/pci/hotplug/pciehp_hpc.c:788)
[ 37.238085] ? __pfx_pciehp_ist (drivers/pci/hotplug/pciehp_hpc.c:728)
[ 37.238091] irq_thread_fn (kernel/irq/manage.c:1131)
[ 37.238098] irq_thread (./arch/x86/include/asm/bitops.h:206
./arch/x86/include/asm/bitops.h:238
./include/asm-generic/bitops/instrumented-non-atomic.h:142
kernel/irq/manage.c:1244)
[ 37.238104] ? __pfx_irq_thread_fn (kernel/irq/manage.c:1130)
[ 37.238110] ? __pfx_irq_thread (kernel/irq/manage.c:1233)
[ 37.238115] ? __pfx_irq_thread_dtor (kernel/irq/manage.c:1167)
[ 37.238123] ? __kthread_parkme (./arch/x86/include/asm/bitops.h:206
./arch/x86/include/asm/bitops.h:238
./include/asm-generic/bitops/instrumented-non-atomic.h:142
kernel/kthread.c:290)
[ 37.238130] ? __pfx_irq_thread (kernel/irq/manage.c:1233)
[ 37.238136] ? __pfx_irq_thread (kernel/irq/manage.c:1233)
[ 37.238141] kthread (kernel/kthread.c:463)
[ 37.238147] ? __pfx_kthread (kernel/kthread.c:412)
[ 37.238153] ? finish_task_switch.isra.0
(./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:119
kernel/sched/sched.h:1531 kernel/sched/core.c:5105 kernel/sched/core.c:5223)
[ 37.238161] ? __pfx_kthread (kernel/kthread.c:412)
[ 37.238166] ret_from_fork (arch/x86/kernel/process.c:154)
[ 37.238175] ? __pfx_kthread (kernel/kthread.c:412)
[ 37.238180] ? __pfx_kthread (kernel/kthread.c:412)
[ 37.238184] ret_from_fork_asm (arch/x86/entry/entry_64.S:258)
[ 37.238192] </TASK>
Suggested-by: Lukas Wunner <lukas@xxxxxxxxx>
Reviewed-by: Lukas Wunner <lukas@xxxxxxxxx>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Acked-by: Rafael J. Wysocki <rafael@xxxxxxxxxx>
Signed-off-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
---
v6:
* rebase on v6.17-rc1
v5:
* Pick up tags, rebase on linux-next
* https://lore.kernel.org/linux-pci/20250709205948.3888045-1-superm1@xxxxxxxxxx/T/#mbd784f786c50a3d1b5ab1833520995c01eae2fd2
---
drivers/pci/pci.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b0f4d98036cdd..036511f5b2625 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1374,6 +1374,11 @@ int pci_power_up(struct pci_dev *dev)
return -EIO;
}
+ if (pci_dev_is_disconnected(dev)) {
+ dev->current_state = PCI_D3cold;
+ return -EIO;
+ }
+
pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
if (PCI_POSSIBLE_ERROR(pmcsr)) {
pci_err(dev, "Unable to change power state from %s to D0, device inaccessible\n",
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
--
2.43.0
