module reentrancy

From: Al Peat (al_kernel@yahoo.com)
Date: Fri Oct 06 2000 - 12:27:28 EST


  I could use a little advice on reentrancy issues for
modules.

  I have written a device driver that is nothing more
than a circular FIFO buffer in memory. The read and
write methods access user space, so I know that those
sections of code need to be reentrant. Since the
module represents one shared buffer, I use a couple of
global variables to keep track of the begin and end of
the buffer. I understand that the filp->private field
provides some protection for reentrancy, but don't
know if that is appropriate in this case. Would a
rwlock be a good solution? The buffer is going to be
used to collect some information from a modified IDE
subsystem, so it will be written to many times in
short periods of time, and thus needs to have
efficient write methods.

  I've read all I could find on reentrancy in the
kernel docs and in Alessandro Rubini's excellent book.
 Any other pointers to things I could read (or good
examples of reentrant modules) would be appreciated.

  Thanks,
        Al

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