-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Brooke,
On 6/1/12 11:54 AM, Hedrick, Brooke - 43 wrote: >> -----Original Message----- From: Christopher Schultz >> [mailto:ch...@christopherschultz.net] Sent: Thursday, May 31, >> 2012 5:23 PM > > That's what I will submit to commons-dbcp, then. > >> On the one hand, synchronizing these methods should not be >> necessary because Java boolean values are defined to be 32-bit >> integers which feature atomic assignment (that is, no thread ever >> sees only 8-bits of the 32-bit value being assigned and 24-bits >> of the old value). On the other hand, threads are allowed to keep >> cached copies of certain data under certain conditions. Using the >> keyword 'volatile' /should/, in recent JVMs, make the use of >> 'synchronized' completely unnecessary, while older JVMs may even >> ignore 'volatile' making 'synchronized' mandatory. Use of >> 'synchronized' is the safest bet because it definitely causes a >> 'memory barrier' to be crossed in any version of JVM: that means >> that the thread is required to synchronize (perhaps a bad choice >> of words) its cache with main memory which means that all >> variables get the latest copies of the "real" data. > > Yep. That was my point too. What does it really matter anyway > whether you are able to lock "this" in a getter. When you ask > for the value, you are just asking for what is current. You have > to protect yourself from non-initialized/null in any case. It just > adds some unnecessary overhead ( to the JVM and brain ) to > synchronize your getter when it doesn't mutate the data - unless I > am missing something. Locking "this" makes sure that the thread's local copy of whatever-you-are-getting is updated properly and not stale-cached. If you synchronize the setter, it is a very good idea to synchronize the getter too. - -chris -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.17 (Darwin) Comment: GPGTools - http://gpgtools.org Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk/I6xcACgkQ9CaO5/Lv0PA87wCeLBo6OzS2H/oEq9pEEduhYNnV xFEAn1sPEI8bUvvC2HSQKKb9Z5tpMQ4b =vMfh -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
