I'm unsure about this usage of the timer (callout(?) )
how does the timer know which buffer pages to remove?
and if each userspace process does an ioctl to allocate a different buffer,
are
the new pages also visible to other processes?
Use mmap() we can ensure different process access different buffer in user
space without
interference.
in FreeBSD your driver can register with at_exit() in 4.x
and with eventhandler_register() in 5.x or 6.x to have stuff done
when the process exits.
Yes, I use this macro and register my handler.
(there are also at_fork and at_exec handlers too.)
see man at_exit (etc.) in 4.x
and man 9 EVENTHANDLER in 5.x and 6.x
You could also make a hash table on the PID so that you keep different
information
available for different processes and look them up
using curproc->p_pid (for 4.x) and curthhread->td_proc->p_pid for 5.x and
6.x
to look up the
Using these primatives you should be able to simulate what you need I
believe.
In FreeBSD, the driver works in the same pattern, but when a user process
mmap driver's buffer (allocated by contigmalloc()) and is killed, then
when
another process mmap the same buffer again, sometimes it cannot get
correct
data from the mmaped pages, which means the user space virtual aderess may
not point to the correct physical page of driver's buffer, sometimes the
OS
even panic with some information such as "Trap 12, Page not present" etc.
sounds like you are getting the buffers confused..
are you doing correc treference counting on the buffers?
In Linux, before kernel memory is mmap to user space, memory pages must be
set a reserved flag, no corresponding operations in FreeBSD, is it right?
And recently, I modified my driver, I allocated a big chunk of contiguous
physical memory using contigmalloc() in the driver's _attach() function,
and I use a simple first-fit algorithm to manage this memory myself, which
mean in ioctl() I use my allocate/deallocate functions instead of
contigmalloc(),
in _detach() function contigfree() is called to free the big chunk of
memory,
no panic again, but sometimes, process cannot get the correct data from
the mmaped memory. I don't know why.
it does sound a bit like you are not keeping the information
separated between processes enough.
I find a bug in my test program, because the big chunk memory in my driver
is reused by new process, but it don't zero it before using it, so some data
last process set interfere the new process.
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