Libor Michalek wrote:
The problem we were seeing is that the minor fault by the app resulted
in a new physical page getting mapped for the application. The page that
had the elevated refcount was still waiting for the data to be written
to by the driver at the time that the app accessed the page causing the
minor fault. Obviously since the app had a new mapping the data written
by the driver was lost.
Thanks Libor, this is much better explanation of the problem than what I posted.
It looks like code was added to try_to_unmap_one() to address this, so
hopefully it's no longer an issue...
I doubt it. I tried this with an earlier 2.6 kernel, and get_user_pages() was still not
enough to really pin the memory down. Maybe it works in 2.6.12, but that doesn't help me
any, because our driver needs to support all 2.4 and 2.6 kernels. Currently, mlock()
alone seems to be good enough, but I'm going to add calls to get_user_pages() just to be sure.
--
Timur Tabi
Staff Software Engineer
[email protected]
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