On 03/24/2014 06:52 PM, Martin Buchholz wrote:
On Wed, Mar 12, 2014 at 1:45 AM, Peter Levart <peter.lev...@gmail.com <mailto:peter.lev...@gmail.com>> wrote:What would the following cost? private transient String stringCache; public String toString() { String sc = stringCache; if (sc == null) { sc = (String) U.getObjectVolatile(this, STRING_CACHE_OFFSET); if (sc == null) { sc = layoutChars(true); if (!U.compareAndSwapObject(this, STRING_CACHE_OFFSET, null, sc)) { sc = (String) U.getObjectVolatile(this, STRING_CACHE_OFFSET); } } } return sc; }I feel I'm missing something. If read -> volatile read -> CAS works, then why wouldn't read -> CAS work and be slightly preferable, because "races are unlikely"?public String toString() { String sc = stringCache; if (sc == null) { sc = layoutChars(true);if (!U.compareAndSwapObject(this, STRING_CACHE_OFFSET, null, sc)) { sc = (String) U.getObjectVolatile(this, STRING_CACHE_OFFSET);} } return sc; }
...yeah, I thought about that too. In any case, the overhead of volatile re-read is negligible in this case, since it happens on slow-path and it might reduce the chance of superfluos calls to layoutChars.
Regards, Peter
