[pypy-commit] stmgc default: Add description

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: 
Changeset: r1178:3f334984ef30
Date: 2014-04-23 09:43 +0200
http://bitbucket.org/pypy/stmgc/changeset/3f334984ef30/

Log:	Add description

diff --git a/c7/stm/core.h b/c7/stm/core.h
--- a/c7/stm/core.h
+++ b/c7/stm/core.h
@@ -151,7 +151,10 @@
     /* This lock is acquired when that segment calls synchronize_object_now.
        On the rare event of a page_privatize(), the latter will acquire
        all the locks in all segments.  Otherwise, for the common case,
-       it's cheap. */
+       it's cheap.  (The set of all 'privatization_lock' in all segments
+       works like one single read-write lock, with page_privatize() acquiring
+       the write lock; but this variant is more efficient for the case of
+       many reads / rare writes.) */
     uint8_t privatization_lock;
 
     /* In case of abort, we restore the 'shadowstack' field and the