lkml.org 
[lkml]   [2010]   [Jun]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] Fix a race in pid generation that causes pids to be reused immediately.
    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).



    \
     
     \ /
      Last update: 2010-06-15 04:01    [W:4.549 / U:0.372 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site