RE: [BUG] usb: xhci: Two possible sleep-in-atomic-context bugs

[Peter Chen]

> 
> The driver may sleep with holding a spinlock.
> The function call paths (from bottom to top) in Linux-4.16.7 are:
> 
> [FUNC] schedule
> drivers/base/power/runtime.c, 741: schedule in rpm_resume
> drivers/base/power/runtime.c, 1322: rpm_resume in pm_runtime_forbid
> drivers/usb/host/xhci-hub.c, 647: pm_runtime_forbid in xhci_enter_test_mode
> drivers/usb/host/xhci-hub.c, 632: _raw_spin_lock_irqsave in xhci_enter_test_mode
> 
> [FUNC] schedule
> drivers/base/power/runtime.c, 570: schedule in rpm_suspend
> drivers/base/power/runtime.c, 434: rpm_suspend in rpm_idle
> drivers/base/power/runtime.c, 1343: rpm_idle in pm_runtime_allow
> drivers/usb/host/xhci-hub.c, 670: pm_runtime_allow in xhci_exit_test_mode
> drivers/usb/host/xhci-hub.c, 1387: xhci_exit_test_mode in xhci_hub_control
> drivers/usb/host/xhci-hub.c, 1038: _raw_spin_lock_irqsave in xhci_hub_control
> 
> These bugs are found by my static analysis tool (DSAC-2) and checked by my code
> review.
> 

I don't think runtime PM API is needed at xhci_hub_control since the controller should
be always active, Mathias, do you agree I delete pm_runtime_forbid and pm_runtime_allow 
to fix this issue?

Peter