On 2018/9/11 15:49, Sebastian Andrzej Siewior wrote:
On 2018-09-01 16:12:10 [+0800], Jia-Ju Bai wrote:
wdm_in_callback() is a completion handler function for the USB driver.
So it should not sleep. But it calls service_outstanding_interrupt(),
which calls usb_submit_urb() with GFP_KERNEL.
At which point does wdm_in_callback() invoke
service_outstanding_interrupt()? I don't see it. I see one invocation
from wdm_read() and another from service_interrupt_work().
Also, if that would be the case, then spin_unlock_irq() in an USB
completion handler (which might run in IRQ context with interrupts
disabled) would be wrong.
Yes, you are right.
I checked an old kernel version Linux-4.16 and got this report.
The current code looks much different from the code that I checked.
Sorry for my false report, and thanks for your correction.
Best wishes,
Jia-Ju Bai
