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Date:      Fri, 19 May 2017 10:24:58 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-usb@FreeBSD.org
Subject:   [Bug 219220] syscalls (ioctls) on USB devices are very slow
Message-ID:  <bug-219220-17-62qvsNHWey@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-219220-17@https.bugs.freebsd.org/bugzilla/>
References:  <bug-219220-17@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D219220

--- Comment #35 from Hans Petter Selasky <hselasky@FreeBSD.org> ---
Hi,

Each USB device instance has a global SX lock. This lock is held during det=
ach.
usbconfig also acquire this lock. If the USB detach cannot complete, because
character devices towards user-space cannot be destroyed, because user-space
apps via libusb keep file /dev/ugenX.Y handles open, then enumeration will
appear frozen until this situation is resolved?

Is that more clear?

--HPS

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