Hi Greg, this is the first of a series of patches that replace the
per-file semaphore ps->devsem with the per-device semaphore
ps->dev->serialize.  The role of devsem was to protect against
device disconnection.  This can be done equally well using
ps->dev->serialize.  On the other hand, ps->dev->serialize
protects against configuration and other changes, and has
already been introduced into usbfs in several places.  Using
just one semaphore simplifies the code and removes some
remaining race conditions.  It should also fix the oopses some
people have been seeing.  In this first patch, a reference is
taken to the usb device as long as the usbfs file is open.  That
way we can use ps->dev->serialize for as long as ps exists.

 devio.c |   27 ++++++++++++++++-----------
 inode.c |    3 ---
 2 files changed, 16 insertions(+), 14 deletions(-)