[linux-usb-devel] [PATCH 1/9] USB usbfs: take a reference to the usb device

[linux-usb-devel] [PATCH 1/9] USB usbfs: take a reference to the usb device

Post by Alan Ster » Mon, 19 Apr 2004 23:50:08



There was a lengthy discussion about this a few months ago. On the whole,
people felt that using an rwsem wasn't a good idea.

Personally, I think that contention for a single device will be very rare,
so we don't need to consider it and can leave things as they are.

Alan Stern

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[linux-usb-devel] [PATCH 1/9] USB usbfs: take a reference to the usb device

Post by David Brow » Wed, 21 Apr 2004 02:30:13

Heh ... I like this, getting rid of more of locks from usbcore.




That doesn't bother me (unlike some folk!) but I do
agree it should wait until the rest shakes out, and
until we can observe benefits. Hardly any code paths
need complete mutual exclusion (writelock).



Actually at least some of those lower levels are getting
fixed by pushing the lock acquisition up.

The reason usbfs needs to get involved in that stuff is
that it's going around the standard usb driver structure.
One of the other things that "usbfs2" should do is act a
lot more like a "normal" device driver, so it plays better
with more of the normal usbcore mechanisms.

- Dave


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