lockref: Relax in cmpxchg loop

While we are likley to succeed and break out of this loop, it isn't
guaranteed.  We should be power and thread friendly if we do have to
go around for a second (or third, or more) attempt.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/lockref.c b/lib/lockref.c
index 7819c2d1d315eff9a010b989d716f1b46387ef4e..9d76f404ce9a6589e7e5b98733d7317b0ad5bb1a 100644 (file)
--- a/lib/lockref.c
+++ b/lib/lockref.c
@@ -19,6 +19,7 @@
                if (likely(old.lock_count == prev.lock_count)) {                \
                        SUCCESS;                                                \
                }                                                               \
+               cpu_relax();                                                    \
        }                                                                       \
 } while (0)