> Let's clarify something, did you run your testcase that triggered this > bug on a v8 or a v9 machine?
Sun UltraSPARC, so V9 of course. The point is that Solaris is TSO (TSO as defined for the V9 architecture, i.e. backward compatible with V8) so you have a V8-compatible TSO implementation, in particular not a Strong Consistency V8. It is perfectly valid to compile with -mcpu=v8 on Solaris and expect to get a working program. Now if you start to play seriously with __sync_synchronize, you conclude that it doesn't implement a full memory barrier with -mcpu=v8. The V8 architecture manual is quite clear about it: TSO allows stores to be reordered after subsequent loads (it's the only difference in TSO with Strong Consistency) so you need to do something to have a full memory barrier. As there is no specific instruction to that effect in V8, you need to do what is done for pre-SSE2 x86, i.e. use an atomic instruction. -- Eric Botcazou
