Re: [PATCH] Fix a race in pid generation that causes pids to be reused immediately.

tytso
2010-06-15T00:56:25Z

On Mon, Jun 14, 2010 at 04:58:51PM -0700, Andrew Morton wrote:
> Using
>
> grep -r '[ ]cmpxchg[^_]' . | grep -v /arch/
>
> I can't see any cmpxchg() callers in truly generic code. lockdep and
> kernel/trace/ring_buffer.c aren't used on the more remote
> architectures, I think.

What about:

drivers/gpu/drm/drm_lock.c: prev = cmpxchg(lock, old, new);
kernel/lockdep.c: n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->de
kernel/sched_clock.c: if (cmpxchg64(&scd->clock, old_clock, clock) != old_cloc
fs/btrfs/inode.c: if (cmpxchg(&root->orphan_cleanup_state, 0, ORPHAN_CLEAN
fs/ext4/inode.c: } while (cmpxchg(&ei->i_flags, old_fl, new_fl) != old_fl

The last is quite new --- I had just recently done a similar set of
research as you did before accepting the patch that added cmpxchg into
ext4 (during the last merge window), and I thought cmpxchg() had
entered the "supported by all architectures" category. It looked like
it had only recently reached state, but I had reached the conclusion
that it was safe to use.

- Ted