Re: [RFC] [PATCH] tapset to count number open file handlers and max file handlers for a process

["Frank Ch. Eigler" <fche at redhat dot com>]

Hi -

On Thu, Aug 30, 2007 at 07:27:47PM +0530, Srinivasa Ds wrote:
> [...]
> > There is at least one problem: all the pointer dereferences are
> > unprotected.  Please use kread() for every link in the pointer chain,
> > in anticipation that every pointer might be corrupt.
> 
> Done

Thanks, but not quite: *every link* needs to be protected.  For
example, this expression has three, so you'll need temporary variables
or more nesting/casting:

> THIS->__retvalue = kread(&(t->files->fdt->max_fds));


> [...]  I have used rcu_read_lock(), thinking it will not harm the
> code (Please correct me if Iam wrong).

Yeah, I think that will work.


> We can even consider putting comment, if we have problem with the
> locks.

That's the wrong way around - we should err on the side of adding
comments if we even speculate about a potential problem.


> > Finally, for a real check-in, one would need documentation in stapfuncs
> > and at least a buildok item in the test suite.
> 
> I am ready to work on this.

Great.

- FChE