Hi, (it helps if you Cc the maintainer too :-)
On Tue, Mar 31, 2015 at 07:53:39PM +0100, Baxter, Jim wrote: > I have been looking at an issue where a phone that is the Function FS > host sometimes locks up and causes the function: which USB controller ? which kernel ? which platform ? > static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data > *io_data) in drivers/usb/gadget/function/f_fs.c to timeout after > MAX_SCHEDULE_TIMEOUT jiffies. yeah, that's pretty much "never timeout" :-) > We are opening the ffs connection with the O_NONBLOCK option and this > timeout seems to be far too long. is this your own application ? How can I make sure it's correct ? > The code causing the wait is here (line 834): > > if (unlikely(ret < 0)) { > /* nop */ > } else if (unlikely( > wait_for_completion_interruptible(&done))) { right, this is waiting for the previous usb_ep_queue() to complete. Why hasn't it completed yet ? Do you have a USB sniffer to check if data has passed over the wire ? Did the host shifted any token in the wire trying to move data around ? > ret = -EINTR; > usb_ep_dequeue(ep->ep, req); > } else { > > The function call wait_for_completion_interruptible(&done) equates to: > wait_for_completion_interruptible_timeout(&done, MAX_SCHEDULE_TIMEOUT); > > > I was wondering what to change to fix this, is it reasonable to use a > very small timeout if it is O_NONBLOCK or is any blocking not allowed? > > I would appreciate any thoughts on how this should work? sounds like a bug on your USB peripheral controller driver. Which one is that ? Again, which kernel ? Where are the logs ? regards -- balbi
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