Messages in this thread | | | Date | Mon, 14 Jun 2010 18:55:56 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] Fix a race in pid generation that causes pids to be reused immediately. |
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On Mon, 14 Jun 2010 20:56:19 -0400 tytso@mit.edu wrote:
> 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
I put these in the not-used-on-weird-architectures bucket.
> kernel/sched_clock.c: if (cmpxchg64(&scd->clock, old_clock, clock) != old_cloc
I guess that'll flush out any stragglers.
I suspect sched_clock.c might be generating fair amounts of code which UP builds don't need.
> 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.
I think you're probably right, as long as one sticks with 4-byte scalars. The cmpxchg-is-now-generic change snuck in under the radar (mine, at least).
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