suspend broken when disconnecting an usb audio device

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Hi, I'm using FreeBSD 10.2-RELEASE-p5 amd64 on a thinkpad t430.

I have suspend and resume functionality working by using newcons and i915kms.ko as the video driver, but whenever I plug in and use my usb DAC, either by choosing it in applications supporting OSS or by setting it as the hw.snd.default_unit and then disconnect it without terminating the audio applications, I can't enter acpi s3.

When trying to suspend the system I get repeated messages on the console: "Waiting for sound application to exit!" (as documented here: http://baitisj.blogspot.it/2015/05/usb-audio-disconnect-woes-in-freebsd.html) but I can't react by killing the incriminated pid since ttys are already unavailable, and I'm forced to perform an hard reset