2021년 8월 9일 (월) 오전 10:27, Peter Chen <peter.chen@xxxxxxxxxx>님이 작성: > > On 21-08-04 11:03:44, Jeaho Hwang wrote: > > Hi. linux-usb and linux-rt experts. > > > > > > On 21-08-02 17:35:01, Jeaho Hwang wrote: > > > > Hi. > > > > > > > > We found an infinite loop inside the function hw_ep_set_halt > > > > (drivers/usb/chipidea/udc.c) if a cablle is repeatedly > > > > connnected/disconnected while ping through RNDIS with chipidea USB device. > > > > > > > > Using ftrace tracing, we found that hw_ep_set_halt is called due to error > > > > return of hw_ep_prime(drivers/usb/chipidea/udc.c:202) which is called from > > > > isr_tr_complete_handler -> isr_setup_status_phase -> _ep_queue. > > > > > > > > The comment of function hw_ep_prime says (execute without interruption) but > > > > timer interrupt is occurred while hw_ep_prime is executing. We believe that > > > > the interrupt causes an error return of hw_ep_prime. We tried to protect > > > > hw_ep_prime from irqs and then no case of the infinite loop is occurred. > > > > > > > > I want ask if it is appropriate way that turning off irq inside (threaded) > > > > irq handlers. And should we explicitly turn off irqs before calling > > > > hw_ep_prime? > > > > > > > > > > Jeaho, do you use RT-Linux or standard Linux? The function hw_ep_prime is > > > only called at udc_irq which is registered as top-half irq handlers. > > > Why the timer interrupt is occurred when hw_ep_prime is executing? > > > > We use preempt_RT so timer interrupt could be occurred. Now I found > > out that forced threaded irq handler disables local irq on standard > > linux so It is a linux-rt issue. Then should I make patch which > > disables local irqs during hw_ep_prime for RT kernel and suggest it to > > linux-rt maintainers? > > > > Thanks for a kind answer Peter. > > > Thanks Peter. > No, that will lead to deadlock since the normal request queue API function > ep_queue disables irq which also calls into hw_ep_prime. ep_queue disables irq by calling spin_lock_irqsave but it actually does not disable irq for RT kernel. Therefore local_irq_save at hw_ep_prime would not cause deadlock if ep_queue calls it, i think. Is it anything wrong? > > For RT kernel, you may try to disable local irq at isr_setup_status_phase. > > -- > > Thanks, > Peter Chen > -- 황재호, Jay Hwang, linux team manager of RTst 010-7242-1593
