On Sat, 2021-10-30 at 14:20 +0000, Joakim Tjernlund wrote: > On Fri, 2021-10-29 at 17:14 +0000, Eugene Bordenkircher wrote: > > Hello all, > > > > We've discovered a situation where the FSL udc driver > > (drivers/usb/gadget/udc/fsl_udc_core.c) will enter a loop iterating over > > the request queue, but the queue has been corrupted at some point so it > > loops infinitely. I believe we have narrowed into the offending code, but > > we are in need of assistance trying to find an appropriate fix for the > > problem. The identified code appears to be in all versions of the Linux > > kernel the driver exists in. > > > > The problem appears to be when handling a USB_REQ_GET_STATUS request. The > > driver gets this request and then calls the ch9getstatus() function. In > > this function, it starts a request by "borrowing" the per device > > status_req, filling it in, and then queuing it with a call to > > list_add_tail() to add the request to the endpoint queue. Right before it > > exits the function however, it's calling ep0_prime_status(), which is > > filling out that same status_req structure and then queuing it with another > > call to list_add_tail() to add the request to the endpoint queue. This > > adds two instances of the exact same LIST_HEAD to the endpoint queue, which > > breaks the list since the prev and next pointers end up pointing to the > > wrong things. This ends up causing a hard loop the next time nuke() gets > > called, which happens on the next setup IRQ. > > > > I'm not sure what the appropriate fix to this problem is, mostly due to my > > lack of expertise in USB and this driver stack. The code has been this way > > in the kernel for a very long time, which suggests that it has been > > working, unless USB_REQ_GET_STATUS requests are never made. This further > > suggests that there is something else going on that I don't understand. > > Deleting the call to ep0_prime_status() and the following ep0stall() call > > appears, on the surface, to get the device working again, but may have side > > effects that I'm not seeing. > > > > I'm hopeful someone in the community can help provide some information on > > what I may be missing or help come up with a solution to the problem. A > > big thank you to anyone who would like to help out. > > > > Eugene > > Run into this to a while ago. Found the bug and a few more fixes. > This is against 4.19 so you may have to tweak them a bit. > Feel free to upstream them. > > Jocke
Curious, did my patches help? Good to known once we upgrade as well. Jocke
