On Thu, 14 Apr 2016, Matthew Giassa wrote: > I should also note that these "control" r/w calls are made very > frequently. A thread is spawned for each camera that periodically polls > for things like exposure levels, average brightness, etc, to update a > metrics cache and UI display for said metrics. That sounds like a disastrous recipe. Instead of using a mutex, you should consider creating a dedicated thread for each camera to handle the control interface. Anybody else that wants to use the control interface should ask the dedicated thread to carry out the I/O on their behalf. That way your program wouldn't constantly be claiming and releasing interfaces. Alan Stern -- 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