Re: [patch 6/12] hold atomic kmaps across generic_file_read

Rusty Russell
2002-08-12T08:17:27Z

On Fri, 9 Aug 2002 18:33:09 -0700 (PDT)
Linus Torvalds <torvalds@transmeta.com> wrote:

> repeat:
> kmap_atomic(..); // this increments preempt count
> nr = copy_from_user(..);

Please please please use a different name for "I know I'm not preemptible but
I can handle it" or a flag or something.

That leaves us with the possibility of a BUG() in the "normal" copy_to/from_user
for all those "I'm holding a spinlock while copying to userspace wheeee!" bugs.
Very common mistake for new kernel authors.

With the preempt count we have an easy way of detecting this at runtime: I'd
like to keep that.

Rusty.
--
there are those who do and those who hang on and you don't see too
many doers quoting their contemporaries. -- Larry McVoy