On Mon, 17 Feb 2014, Stanislaw Gruszka wrote: > There is threadirqs kenel boot option which allow to force interrupt > routines to be performed as thread. > > USB irq routines use spin_lock(*hci->lock) variant without disabling > interrupts, what is perfectly fine, but that can cause deadlock when > forced thread irqs are used. Deadlock scenario is quite reproducible for > me, as I can not boot system with threadirqs option, when some USB > device is connected. Patch marks USB irq routines with IRQF_NO_THREAD > to prevent forced threading. This doesn't explain the entire story. As far as we know the deadlock affects only ehci-hcd, because only ehci-hcd uses an hrtimer callback, and hrtimer callbacks run in interrupt context even when threadirqs is specified. Maybe the patch should include a comment explaining that the IRQF_NO_THREAD flag will not be needed when hrtimer callbacks are threaded. 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
