Hello, On Tuesday, June 23, 2009 9:23 AM, David Brownell wrote: > > > Like, oh, changing a spinlock to a mutex. You might change the > > > low_latency setting and review how that's now supposed to behave. > > > > In in gs_open() function in drivers/usb/gadget/u_serial.c, after the > > line 780 I've added: > > > > tty->low_latency = 1; > > That's already how it's set. Try instead *REMOVING* the line > which sets that flag. My fault. I didn't notice that a few lines lower the low_latency flag is alredy set and I thought I should set it. After removing that, g_serial started working. :) Thanks a lot. I noticed that there is also a comment: /* low_latency means ldiscs work in tasklet context, without * needing a workqueue schedule ... easier to keep up. */ So in low latency mode calls are made from a tasklet. This is not true in my case, as the S3C OTG UDC driver does all its job in interrupts. This way also a (usb) packet_done callback is done from an interrupt. I expect that g_serial driver interacts with tty layer in that packet_done callback, so this is the source of the problems. I noticed that some other UDC drivers also does all its job from an interrupt, so they also might be affected. How this bug should be properly resolved? Best regards -- Marek Szyprowski Samsung Poland R&D Center -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
