Freeing mmapped memory

[John-Mark Gurney]

Raaf wrote this message on Mon, Feb 06, 2006 at 22:54 +0100:
> Hi, i am working on a usb driver that allocates some memory when
> the device is opened using malloc.
> 
> Now i want user processes to be able to access this memory using
> mmap and i want to free this memory when it is no longer needed.
> 
> The problem is that there seems to be no way of knowing for my
> driver at what time the memory is no longer mapped in a process
> address space so that i can safely free this memory.

why not at close time?  I would imagine that the device won't be closed
until all the mmap's that are backed by the device are unmapped..  it
shouldn't be hard to test...  the mapping should hold a reference to
the device until it's munmapped..

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."