On Fri, Jul 24, 2009 at 07:47:30PM -0400, Jay Pipes wrote: > OK, so, I've tracked down the issue I was having with the replication > branch to a difference in behaviour in atomic<> variables on CentOS > (osindriz03) vs. other machines...hoping someone has an answer. > > Here is the code which is behaving differently depending on the platform: > > log_offset is declared as drizzled::atomic<off_t>. > > log_offset= 0; > uint64_t length= 42; > > off_t cur_offset; > > cur_offset= log_offset.fetch_and_add((sizeof(uint64_t) + length)); > > On ALL other platforms other than CentOS 5, the above code sets > log_offset AND cur_offset equal to 50. > > On CentOS, it sets log_offset to 50 and cur_offset to 0. > > What does this mean? It means that the assignment to cur_offset is > happening *before* the call to drizzled::atomic<off_t>::fetch_and_add(). > > Without resorting back to mutexes, I am uncertain how to solve this > particular timing/atomics problem. I'm hoping someone out there has > more experience dealing with this.
Is this repeatable just in a single thread? small test program? i think it'd be useful to look at the disassembled binary produced (and, well, diff them :) I have a few theories in my head, but will have to look more closely (when not really hanging out for lunch and lebanese coffee on a saturday :) but if you can get me binaries from both machines, preferably even ssh access, and point me at the right branch, will have a go. -- Stewart Smith _______________________________________________ Mailing list: https://launchpad.net/~drizzle-discuss Post to : [email protected] Unsubscribe : https://launchpad.net/~drizzle-discuss More help : https://help.launchpad.net/ListHelp
