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Re: kern/51524: USB vs. serial problems

The following reply was made to PR kern/51524; it has been noted by GNATS.

From: David Holland <>
Subject: Re: kern/51524: USB vs. serial problems
Date: Mon, 3 Oct 2016 00:38:51 +0000

 On Sun, Oct 02, 2016 at 10:15:00PM +0000, John D. Baker wrote:
  >  > 4 hours later I saw the following in the kernel log:
  >  >ehci_sync_hc: cv_timedwait() = 35
  >  Curious.  This exact same error has been observed with USB network
  >  devices [...]
 I just changed it so it will print
    ehci_sync_hc: timed out
 which is no more helpful but less mysterious.
 It seems that ehci_sync_hc pokes the ehci and tells it to send an
 interrupt when it's done (with something-or-other) and then waits; the
 print means that the interrupt didn't happen after one second.
 I notice though that ehci_device_intr_abort() says this:
     * XXX - abort_xfer uses ehci_sync_hc, which syncs via the advance
     *       async doorbell. That's dependent on the async list, wheras
     *       intr xfers are periodic, should not use this?
    ehci_abort_xfer(xfer, USBD_CANCELLED);
 and I wonder if that's part of the problem...
 David A. Holland

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